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	$93.85	12.245%	$105.3419	$105.34	$105.35	$105.30
Purchase #2	$134.41	11.344%	$149.6575	$149.66	$149.65	$149.70
Purchase #3	$246.31	10.336%	$271.7686	$271.77	$271.75	$271.80
Purchase #4	$19.53	5.196%	$20.5448	$20.54	$20.55	$20.50
Purchase #5	$193.67	11.648%	$216.2287	$216.23	$216.25	$216.20
Purchase #6	$73.92	10.773%	$81.8834	$81.88	$81.90	$81.90
Purchase #7	$211.43	5.660%	$223.3969	$223.40	$223.40	$223.40
7 purchase totals =	$973.12		$1,068.8218	$1,068.82	$1,068.85	$1,068.80