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	$121.33	7.187%	$130.05	$130.05	$130.05	$130.10
Purchase #2	$65.84	9.662%	$72.2015	$72.20	$72.20	$72.20
Purchase #3	$54.86	11.362%	$61.0932	$61.09	$61.10	$61.10
Purchase #4	$83.28	13.573%	$94.5836	$94.58	$94.60	$94.60
Purchase #5	$23.46	6.281%	$24.9335	$24.93	$24.95	$24.90
Purchase #6	$213.82	7.313%	$229.4567	$229.46	$229.45	$229.50
Purchase #7	$45.55	6.450%	$48.488	$48.49	$48.50	$48.50
7 purchase totals =	$608.14		$660.8065	$660.80	$660.85	$660.90