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	$126.92	3.116%	$130.8748	$130.87	$130.85	$130.90
Purchase #2	$50.77	3.476%	$52.5348	$52.53	$52.55	$52.50
Purchase #3	$205.90	7.871%	$222.1064	$222.11	$222.10	$222.10
Purchase #4	$197.89	7.248%	$212.2331	$212.23	$212.25	$212.20
Purchase #5	$172.39	7.796%	$185.8295	$185.83	$185.85	$185.80
Purchase #6	$66.89	12.349%	$75.1502	$75.15	$75.15	$75.20
Purchase #7	$156.97	5.854%	$166.159	$166.16	$166.15	$166.20
7 purchase totals =	$977.73		$1,044.8878	$1,044.88	$1,044.90	$1,044.90