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	$61.54	8.751%	$66.9254	$66.93	$66.95	$66.90
Purchase #2	$136.93	7.701%	$147.475	$147.48	$147.50	$147.50
Purchase #3	$53.82	7.474%	$57.8425	$57.84	$57.85	$57.80
Purchase #4	$169.71	5.850%	$179.638	$179.64	$179.65	$179.60
Purchase #5	$48.37	12.449%	$54.3916	$54.39	$54.40	$54.40
Purchase #6	$126.50	4.482%	$132.1697	$132.17	$132.15	$132.20
Purchase #7	$118.72	5.105%	$124.7807	$124.78	$124.80	$124.80
7 purchase totals =	$715.59		$763.2229	$763.23	$763.30	$763.20