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	$146.81	13.559%	$166.716	$166.72	$166.70	$166.70
Purchase #2	$227.33	3.567%	$235.4389	$235.44	$235.45	$235.40
Purchase #3	$134.63	8.777%	$146.4465	$146.45	$146.45	$146.40
Purchase #4	$186.50	13.614%	$211.8901	$211.89	$211.90	$211.90
Purchase #5	$79.38	10.627%	$87.8157	$87.82	$87.80	$87.80
Purchase #6	$97.71	7.835%	$105.3656	$105.37	$105.35	$105.40
Purchase #7	$119.70	4.301%	$124.8483	$124.85	$124.85	$124.80
7 purchase totals =	$992.06		$1,078.5211	$1,078.54	$1,078.50	$1,078.40