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	$241.73	13.238%	$273.7302	$273.73	$273.75	$273.70
Purchase #2	$52.47	10.850%	$58.163	$58.16	$58.15	$58.20
Purchase #3	$32.85	3.155%	$33.8864	$33.89	$33.90	$33.90
Purchase #4	$54.87	4.679%	$57.4374	$57.44	$57.45	$57.40
Purchase #5	$70.68	5.425%	$74.5144	$74.51	$74.50	$74.50
Purchase #6	$206.32	8.364%	$223.5766	$223.58	$223.60	$223.60
Purchase #7	$137.42	12.146%	$154.111	$154.11	$154.10	$154.10
7 purchase totals =	$796.34		$875.4190	$875.42	$875.45	$875.40