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	$244.54	9.397%	$267.5194	$267.52	$267.50	$267.50
Purchase #2	$172.34	11.216%	$191.6697	$191.67	$191.65	$191.70
Purchase #3	$132.47	11.807%	$148.1107	$148.11	$148.10	$148.10
Purchase #4	$59.82	8.766%	$65.0638	$65.06	$65.05	$65.10
Purchase #5	$46.93	11.814%	$52.4743	$52.47	$52.45	$52.50
Purchase #6	$39.49	3.682%	$40.944	$40.94	$40.95	$40.90
Purchase #7	$200.26	9.711%	$219.7072	$219.71	$219.70	$219.70
7 purchase totals =	$895.85		$985.4891	$985.48	$985.40	$985.50