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	$71.70	7.873%	$77.3449	$77.34	$77.35	$77.30
Purchase #2	$123.31	13.269%	$139.672	$139.67	$139.65	$139.70
Purchase #3	$160.63	3.861%	$166.8319	$166.83	$166.85	$166.80
Purchase #4	$137.37	6.816%	$146.7331	$146.73	$146.75	$146.70
Purchase #5	$151.91	6.616%	$161.9604	$161.96	$161.95	$162.00
Purchase #6	$185.62	5.733%	$196.2616	$196.26	$196.25	$196.30
Purchase #7	$250.41	10.144%	$275.8116	$275.81	$275.80	$275.80
7 purchase totals =	$1,080.95		$1,164.6155	$1,164.60	$1,164.60	$1,164.60