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	$127.82	13.601%	$145.2048	$145.20	$145.20	$145.20
Purchase #2	$192.94	11.378%	$214.8927	$214.89	$214.90	$214.90
Purchase #3	$115.67	7.473%	$124.314	$124.31	$124.30	$124.30
Purchase #4	$133.78	13.738%	$152.1587	$152.16	$152.15	$152.20
Purchase #5	$45.78	6.869%	$48.9246	$48.92	$48.90	$48.90
Purchase #6	$172.88	6.485%	$184.0913	$184.09	$184.10	$184.10
Purchase #7	$249.55	11.158%	$277.3948	$277.39	$277.40	$277.40
7 purchase totals =	$1,038.42		$1,146.9809	$1,146.96	$1,146.95	$1,147.00