Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$178.91	6.586%	$190.693	$190.69	$190.70	$190.70
Purchase #2	$221.46	5.278%	$233.1487	$233.15	$233.15	$233.10
Purchase #3	$104.72	6.782%	$111.8221	$111.82	$111.80	$111.80
Purchase #4	$198.30	3.157%	$204.5603	$204.56	$204.55	$204.60
Purchase #5	$86.84	6.337%	$92.3431	$92.34	$92.35	$92.30
Purchase #6	$179.26	13.540%	$203.5318	$203.53	$203.55	$203.50
Purchase #7	$72.97	10.217%	$80.4253	$80.43	$80.45	$80.40
7 purchase totals =	$1,042.46		$1,116.5243	$1,116.52	$1,116.55	$1,116.40