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	$52.58	13.494%	$59.6751	$59.68	$59.70	$59.70
Purchase #2	$224.85	4.579%	$235.1459	$235.15	$235.15	$235.10
Purchase #3	$155.73	10.830%	$172.5956	$172.60	$172.60	$172.60
Purchase #4	$136.46	12.201%	$153.1095	$153.11	$153.10	$153.10
Purchase #5	$98.29	13.823%	$111.8766	$111.88	$111.90	$111.90
Purchase #6	$232.30	11.409%	$258.8031	$258.80	$258.80	$258.80
Purchase #7	$175.85	5.705%	$185.8822	$185.88	$185.90	$185.90
7 purchase totals =	$1,076.06		$1,177.0880	$1,177.10	$1,177.15	$1,177.10