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	$238.67	12.768%	$269.1434	$269.14	$269.15	$269.10
Purchase #2	$40.47	11.848%	$45.2649	$45.26	$45.25	$45.30
Purchase #3	$72.32	6.833%	$77.2616	$77.26	$77.25	$77.30
Purchase #4	$42.64	12.662%	$48.0391	$48.04	$48.05	$48.00
Purchase #5	$204.43	7.369%	$219.4944	$219.49	$219.50	$219.50
Purchase #6	$190.26	11.489%	$212.119	$212.12	$212.10	$212.10
Purchase #7	$79.66	3.327%	$82.3103	$82.31	$82.30	$82.30
7 purchase totals =	$868.45		$953.6327	$953.62	$953.60	$953.60