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	$135.39	11.747%	$151.2943	$151.29	$151.30	$151.30
Purchase #2	$236.74	7.490%	$254.4718	$254.47	$254.45	$254.50
Purchase #3	$227.91	12.204%	$255.7241	$255.72	$255.70	$255.70
Purchase #4	$207.77	7.120%	$222.5632	$222.56	$222.55	$222.60
Purchase #5	$169.61	6.609%	$180.8195	$180.82	$180.80	$180.80
Purchase #6	$67.64	13.223%	$76.584	$76.58	$76.60	$76.60
Purchase #7	$203.56	9.128%	$222.141	$222.14	$222.15	$222.10
7 purchase totals =	$1,248.62		$1,363.5979	$1,363.58	$1,363.55	$1,363.60