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	$132.35	8.742%	$143.92	$143.92	$143.90	$143.90
Purchase #2	$247.98	3.388%	$256.3816	$256.38	$256.40	$256.40
Purchase #3	$57.74	11.468%	$64.3616	$64.36	$64.35	$64.40
Purchase #4	$222.39	4.738%	$232.9268	$232.93	$232.95	$232.90
Purchase #5	$13.42	9.742%	$14.7274	$14.73	$14.75	$14.70
Purchase #6	$91.30	9.136%	$99.6412	$99.64	$99.65	$99.60
Purchase #7	$229.78	11.652%	$256.554	$256.55	$256.55	$256.60
7 purchase totals =	$994.96		$1,068.5126	$1,068.51	$1,068.55	$1,068.50