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	$67.37	7.551%	$72.4571	$72.46	$72.45	$72.50
Purchase #2	$90.98	10.309%	$100.3591	$100.36	$100.35	$100.40
Purchase #3	$177.43	12.363%	$199.3657	$199.37	$199.35	$199.40
Purchase #4	$111.32	10.751%	$123.288	$123.29	$123.30	$123.30
Purchase #5	$218.28	8.254%	$236.2968	$236.30	$236.30	$236.30
Purchase #6	$8.85	9.572%	$9.6971	$9.70	$9.70	$9.70
Purchase #7	$212.54	10.252%	$234.3296	$234.33	$234.35	$234.30
7 purchase totals =	$886.77		$975.7934	$975.81	$975.80	$975.90