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	$203.37	4.315%	$212.1454	$212.15	$212.15	$212.10
Purchase #2	$157.78	11.634%	$176.1361	$176.14	$176.15	$176.10
Purchase #3	$51.86	11.133%	$57.6336	$57.63	$57.65	$57.60
Purchase #4	$222.85	9.403%	$243.8046	$243.80	$243.80	$243.80
Purchase #5	$20.89	7.266%	$22.4079	$22.41	$22.40	$22.40
Purchase #6	$244.75	12.705%	$275.8455	$275.85	$275.85	$275.80
Purchase #7	$59.35	13.608%	$67.4263	$67.43	$67.45	$67.40
7 purchase totals =	$960.85		$1,055.3994	$1,055.41	$1,055.45	$1,055.20