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	$148.63	6.792%	$158.7249	$158.72	$158.70	$158.70
Purchase #2	$141.83	7.298%	$152.1808	$152.18	$152.20	$152.20
Purchase #3	$45.70	6.828%	$48.8204	$48.82	$48.80	$48.80
Purchase #4	$88.79	10.756%	$98.3403	$98.34	$98.35	$98.30
Purchase #5	$164.60	7.850%	$177.5211	$177.52	$177.50	$177.50
Purchase #6	$55.33	7.234%	$59.3326	$59.33	$59.35	$59.30
Purchase #7	$67.75	5.870%	$71.7269	$71.73	$71.75	$71.70
7 purchase totals =	$712.63		$766.6470	$766.64	$766.65	$766.50