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	$70.62	7.812%	$76.1368	$76.14	$76.15	$76.10
Purchase #2	$89.68	3.710%	$93.0071	$93.01	$93.00	$93.00
Purchase #3	$28.86	13.163%	$32.6588	$32.66	$32.65	$32.70
Purchase #4	$81.94	9.753%	$89.9316	$89.93	$89.95	$89.90
Purchase #5	$193.58	12.789%	$218.3369	$218.34	$218.35	$218.30
Purchase #6	$37.33	9.549%	$40.8946	$40.89	$40.90	$40.90
Purchase #7	$208.76	7.437%	$224.2855	$224.29	$224.30	$224.30
7 purchase totals =	$710.77		$775.2513	$775.26	$775.30	$775.20