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	$83.56	12.855%	$94.3016	$94.30	$94.30	$94.30
Purchase #2	$101.87	7.589%	$109.6009	$109.60	$109.60	$109.60
Purchase #3	$72.84	7.453%	$78.2688	$78.27	$78.25	$78.30
Purchase #4	$229.80	7.434%	$246.8833	$246.88	$246.90	$246.90
Purchase #5	$42.70	12.725%	$48.1336	$48.13	$48.15	$48.10
Purchase #6	$125.53	9.368%	$137.2897	$137.29	$137.30	$137.30
Purchase #7	$214.72	10.420%	$237.0938	$237.09	$237.10	$237.10
7 purchase totals =	$871.02		$951.5717	$951.56	$951.60	$951.60