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	$170.89	4.581%	$178.7185	$178.72	$178.70	$178.70
Purchase #2	$126.62	3.802%	$131.4341	$131.43	$131.45	$131.40
Purchase #3	$102.97	5.498%	$108.6313	$108.63	$108.65	$108.60
Purchase #4	$77.30	9.604%	$84.7239	$84.72	$84.70	$84.70
Purchase #5	$202.54	12.794%	$228.453	$228.45	$228.45	$228.50
Purchase #6	$101.66	9.521%	$111.339	$111.34	$111.35	$111.30
Purchase #7	$171.85	8.160%	$185.873	$185.87	$185.85	$185.90
7 purchase totals =	$953.83		$1,029.1728	$1,029.16	$1,029.15	$1,029.10