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	$188.79	10.625%	$208.8489	$208.85	$208.85	$208.80
Purchase #2	$124.45	10.187%	$137.1277	$137.13	$137.15	$137.10
Purchase #3	$103.50	5.429%	$109.119	$109.12	$109.10	$109.10
Purchase #4	$123.68	4.125%	$128.7818	$128.78	$128.80	$128.80
Purchase #5	$111.67	9.514%	$122.2943	$122.29	$122.30	$122.30
Purchase #6	$13.48	12.691%	$15.1907	$15.19	$15.20	$15.20
Purchase #7	$215.89	3.544%	$223.5411	$223.54	$223.55	$223.50
7 purchase totals =	$881.46		$944.9035	$944.90	$944.95	$944.80