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	$57.40	8.335%	$62.1843	$62.18	$62.20	$62.20
Purchase #2	$222.63	11.131%	$247.4109	$247.41	$247.40	$247.40
Purchase #3	$60.64	7.404%	$65.1298	$65.13	$65.15	$65.10
Purchase #4	$131.63	11.595%	$146.8925	$146.89	$146.90	$146.90
Purchase #5	$221.94	5.197%	$233.4742	$233.47	$233.45	$233.50
Purchase #6	$121.57	9.410%	$133.0097	$133.01	$133.00	$133.00
Purchase #7	$186.82	3.676%	$193.6875	$193.69	$193.70	$193.70
7 purchase totals =	$1,002.63		$1,081.7889	$1,081.78	$1,081.80	$1,081.80