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	$78.97	3.287%	$81.5657	$81.57	$81.55	$81.60
Purchase #2	$165.29	10.603%	$182.8157	$182.82	$182.80	$182.80
Purchase #3	$177.67	3.664%	$184.1798	$184.18	$184.20	$184.20
Purchase #4	$89.31	11.167%	$99.2832	$99.28	$99.30	$99.30
Purchase #5	$70.80	11.130%	$78.68	$78.68	$78.70	$78.70
Purchase #6	$250.31	7.493%	$269.0657	$269.07	$269.05	$269.10
Purchase #7	$43.83	10.662%	$48.5032	$48.50	$48.50	$48.50
7 purchase totals =	$876.18		$944.0933	$944.10	$944.10	$944.20