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	$106.49	13.567%	$120.9375	$120.94	$120.95	$120.90
Purchase #2	$140.43	7.592%	$151.0914	$151.09	$151.10	$151.10
Purchase #3	$44.59	13.813%	$50.7492	$50.75	$50.75	$50.70
Purchase #4	$149.31	3.130%	$153.9834	$153.98	$154.00	$154.00
Purchase #5	$195.39	6.621%	$208.3268	$208.33	$208.35	$208.30
Purchase #6	$226.54	8.275%	$245.2862	$245.29	$245.30	$245.30
Purchase #7	$73.53	6.312%	$78.1712	$78.17	$78.15	$78.20
7 purchase totals =	$936.28		$1,008.5457	$1,008.55	$1,008.60	$1,008.50