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	$204.91	4.671%	$214.4813	$214.48	$214.50	$214.50
Purchase #2	$39.72	6.465%	$42.2879	$42.29	$42.30	$42.30
Purchase #3	$166.27	7.589%	$178.8882	$178.89	$178.90	$178.90
Purchase #4	$235.36	4.539%	$246.043	$246.04	$246.05	$246.00
Purchase #5	$141.46	5.286%	$148.9376	$148.94	$148.95	$148.90
Purchase #6	$170.95	5.369%	$180.1283	$180.13	$180.15	$180.10
Purchase #7	$151.55	13.117%	$171.4288	$171.43	$171.45	$171.40
7 purchase totals =	$1,110.22		$1,182.1951	$1,182.20	$1,182.30	$1,182.10