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	$42.59	7.304%	$45.7008	$45.70	$45.70	$45.70
Purchase #2	$163.45	5.543%	$172.51	$172.51	$172.50	$172.50
Purchase #3	$61.90	12.369%	$69.5564	$69.56	$69.55	$69.60
Purchase #4	$11.42	3.601%	$11.8312	$11.83	$11.85	$11.80
Purchase #5	$166.51	8.197%	$180.1588	$180.16	$180.15	$180.20
Purchase #6	$214.59	13.142%	$242.7914	$242.79	$242.80	$242.80
Purchase #7	$199.69	5.718%	$211.1083	$211.11	$211.10	$211.10
7 purchase totals =	$860.15		$933.6569	$933.66	$933.65	$933.70