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	$221.44	10.577%	$244.8617	$244.86	$244.85	$244.90
Purchase #2	$42.45	3.754%	$44.0436	$44.04	$44.05	$44.00
Purchase #3	$159.45	13.245%	$180.5692	$180.57	$180.55	$180.60
Purchase #4	$48.82	4.278%	$50.9085	$50.91	$50.90	$50.90
Purchase #5	$242.78	12.516%	$273.1663	$273.17	$273.15	$273.20
Purchase #6	$145.62	13.664%	$165.5175	$165.52	$165.50	$165.50
Purchase #7	$52.66	9.793%	$57.817	$57.82	$57.80	$57.80
7 purchase totals =	$913.22		$1,016.8838	$1,016.89	$1,016.80	$1,016.90