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	$58.29	5.466%	$61.4761	$61.48	$61.50	$61.50
Purchase #2	$56.39	3.829%	$58.5492	$58.55	$58.55	$58.50
Purchase #3	$151.29	5.218%	$159.1843	$159.18	$159.20	$159.20
Purchase #4	$52.89	4.429%	$55.2325	$55.23	$55.25	$55.20
Purchase #5	$230.87	7.385%	$247.9197	$247.92	$247.90	$247.90
Purchase #6	$238.30	12.448%	$267.9636	$267.96	$267.95	$268.00
Purchase #7	$216.45	8.568%	$234.9954	$235.00	$235.00	$235.00
7 purchase totals =	$1,004.48		$1,085.3208	$1,085.32	$1,085.35	$1,085.30