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	$92.54	12.764%	$104.3518	$104.35	$104.35	$104.40
Purchase #2	$136.85	9.438%	$149.7659	$149.77	$149.75	$149.80
Purchase #3	$34.96	3.342%	$36.1284	$36.13	$36.15	$36.10
Purchase #4	$166.31	3.748%	$172.5433	$172.54	$172.55	$172.50
Purchase #5	$208.77	9.388%	$228.3693	$228.37	$228.35	$228.40
Purchase #6	$180.86	5.544%	$190.8869	$190.89	$190.90	$190.90
Purchase #7	$79.66	4.832%	$83.5092	$83.51	$83.50	$83.50
7 purchase totals =	$899.95		$965.5548	$965.56	$965.55	$965.60