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	$41.43	9.743%	$45.4665	$45.47	$45.45	$45.50
Purchase #2	$211.54	7.646%	$227.7143	$227.71	$227.70	$227.70
Purchase #3	$180.76	9.291%	$197.5544	$197.55	$197.55	$197.60
Purchase #4	$48.83	3.632%	$50.6035	$50.60	$50.60	$50.60
Purchase #5	$67.78	6.588%	$72.2453	$72.25	$72.25	$72.20
Purchase #6	$235.75	9.701%	$258.6201	$258.62	$258.60	$258.60
Purchase #7	$105.86	5.493%	$111.6749	$111.67	$111.65	$111.70
7 purchase totals =	$891.95		$963.8790	$963.87	$963.80	$963.90