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	$129.54	6.475%	$137.9277	$137.93	$137.95	$137.90
Purchase #2	$151.72	3.771%	$157.4414	$157.44	$157.45	$157.40
Purchase #3	$248.25	3.352%	$256.5713	$256.57	$256.55	$256.60
Purchase #4	$203.77	13.375%	$231.0242	$231.02	$231.00	$231.00
Purchase #5	$87.39	13.695%	$99.3581	$99.36	$99.35	$99.40
Purchase #6	$129.27	10.267%	$142.5422	$142.54	$142.55	$142.50
Purchase #7	$208.65	7.142%	$223.5518	$223.55	$223.55	$223.60
7 purchase totals =	$1,158.59		$1,248.4167	$1,248.41	$1,248.40	$1,248.40