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	$217.78	11.473%	$242.7659	$242.77	$242.75	$242.80
Purchase #2	$55.39	12.557%	$62.3453	$62.35	$62.35	$62.30
Purchase #3	$157.54	8.549%	$171.0081	$171.01	$171.00	$171.00
Purchase #4	$41.33	4.742%	$43.2899	$43.29	$43.30	$43.30
Purchase #5	$45.67	13.403%	$51.7912	$51.79	$51.80	$51.80
Purchase #6	$158.63	12.501%	$178.4603	$178.46	$178.45	$178.50
Purchase #7	$182.62	9.240%	$199.4941	$199.49	$199.50	$199.50
7 purchase totals =	$858.96		$949.1548	$949.16	$949.15	$949.20