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	$10.29	6.331%	$10.9415	$10.94	$10.95	$10.90
Purchase #2	$40.29	6.229%	$42.7997	$42.80	$42.80	$42.80
Purchase #3	$37.88	9.700%	$41.5544	$41.55	$41.55	$41.60
Purchase #4	$204.41	8.682%	$222.1569	$222.16	$222.15	$222.20
Purchase #5	$136.79	9.369%	$149.6059	$149.61	$149.60	$149.60
Purchase #6	$17.86	9.482%	$19.5535	$19.55	$19.55	$19.60
Purchase #7	$229.91	8.832%	$250.2157	$250.22	$250.20	$250.20
7 purchase totals =	$677.43		$736.8276	$736.83	$736.80	$736.90