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	$238.73	9.401%	$261.173	$261.17	$261.15	$261.20
Purchase #2	$33.67	11.140%	$37.4208	$37.42	$37.40	$37.40
Purchase #3	$69.84	13.444%	$79.2293	$79.23	$79.25	$79.20
Purchase #4	$108.80	10.333%	$120.0423	$120.04	$120.05	$120.00
Purchase #5	$53.95	11.514%	$60.1618	$60.16	$60.15	$60.20
Purchase #6	$243.53	13.146%	$275.5445	$275.54	$275.55	$275.50
Purchase #7	$113.40	13.658%	$128.8882	$128.89	$128.90	$128.90
7 purchase totals =	$861.92		$962.4599	$962.45	$962.45	$962.40