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	$183.99	6.594%	$196.1223	$196.12	$196.10	$196.10
Purchase #2	$50.38	9.283%	$55.0568	$55.06	$55.05	$55.10
Purchase #3	$244.54	4.379%	$255.2484	$255.25	$255.25	$255.20
Purchase #4	$143.34	6.148%	$152.1525	$152.15	$152.15	$152.20
Purchase #5	$72.50	13.448%	$82.2498	$82.25	$82.25	$82.20
Purchase #6	$143.30	12.428%	$161.1093	$161.11	$161.10	$161.10
Purchase #7	$153.96	9.624%	$168.7771	$168.78	$168.80	$168.80
7 purchase totals =	$992.01		$1,070.7162	$1,070.72	$1,070.70	$1,070.70