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	$223.72	13.152%	$253.1437	$253.14	$253.15	$253.10
Purchase #2	$35.65	4.661%	$37.3116	$37.31	$37.30	$37.30
Purchase #3	$10.66	4.850%	$11.177	$11.18	$11.20	$11.20
Purchase #4	$30.69	6.574%	$32.7076	$32.71	$32.70	$32.70
Purchase #5	$79.95	11.631%	$89.249	$89.25	$89.25	$89.20
Purchase #6	$179.48	12.202%	$201.3801	$201.38	$201.40	$201.40
Purchase #7	$206.82	7.689%	$222.7224	$222.72	$222.70	$222.70
7 purchase totals =	$766.97		$847.6914	$847.69	$847.70	$847.60