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	$240.69	7.741%	$259.3218	$259.32	$259.30	$259.30
Purchase #2	$37.64	11.581%	$41.9991	$42.00	$42.00	$42.00
Purchase #3	$192.35	5.157%	$202.2695	$202.27	$202.25	$202.30
Purchase #4	$172.33	10.741%	$190.84	$190.84	$190.85	$190.80
Purchase #5	$135.43	13.792%	$154.1085	$154.11	$154.10	$154.10
Purchase #6	$88.89	5.431%	$93.7176	$93.72	$93.70	$93.70
Purchase #7	$52.75	12.722%	$59.4609	$59.46	$59.45	$59.50
7 purchase totals =	$920.08		$1,001.7174	$1,001.72	$1,001.65	$1,001.70