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	$151.95	13.281%	$172.1305	$172.13	$172.15	$172.10
Purchase #2	$80.88	10.869%	$89.6708	$89.67	$89.65	$89.70
Purchase #3	$149.69	11.834%	$167.4043	$167.40	$167.40	$167.40
Purchase #4	$175.53	8.221%	$189.9603	$189.96	$189.95	$190.00
Purchase #5	$106.88	7.160%	$114.5326	$114.53	$114.55	$114.50
Purchase #6	$145.56	3.321%	$150.394	$150.39	$150.40	$150.40
Purchase #7	$147.97	6.859%	$158.1193	$158.12	$158.10	$158.10
7 purchase totals =	$958.46		$1,042.2118	$1,042.20	$1,042.20	$1,042.20