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	$101.89	9.221%	$111.2853	$111.29	$111.30	$111.30
Purchase #2	$250.43	3.232%	$258.5239	$258.52	$258.50	$258.50
Purchase #3	$248.56	3.742%	$257.8611	$257.86	$257.85	$257.90
Purchase #4	$247.92	8.733%	$269.5709	$269.57	$269.55	$269.60
Purchase #5	$193.40	11.829%	$216.2773	$216.28	$216.30	$216.30
Purchase #6	$175.49	11.700%	$196.0223	$196.02	$196.00	$196.00
Purchase #7	$159.89	5.388%	$168.5049	$168.50	$168.50	$168.50
7 purchase totals =	$1,377.58		$1,478.0457	$1,478.04	$1,478.00	$1,478.10