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	$152.44	4.466%	$159.248	$159.25	$159.25	$159.20
Purchase #2	$111.56	11.782%	$124.704	$124.70	$124.70	$124.70
Purchase #3	$35.96	3.275%	$37.1377	$37.14	$37.15	$37.10
Purchase #4	$35.43	6.649%	$37.7857	$37.79	$37.80	$37.80
Purchase #5	$160.44	8.180%	$173.564	$173.56	$173.55	$173.60
Purchase #6	$117.83	11.643%	$131.5489	$131.55	$131.55	$131.50
Purchase #7	$218.89	5.840%	$231.6732	$231.67	$231.65	$231.70
7 purchase totals =	$832.55		$895.6615	$895.66	$895.65	$895.60