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	$210.37	5.860%	$222.6977	$222.70	$222.70	$222.70
Purchase #2	$247.42	11.851%	$276.7417	$276.74	$276.75	$276.70
Purchase #3	$59.94	10.741%	$66.3782	$66.38	$66.40	$66.40
Purchase #4	$22.75	3.375%	$23.5178	$23.52	$23.50	$23.50
Purchase #5	$37.42	10.362%	$41.2975	$41.30	$41.30	$41.30
Purchase #6	$139.73	13.453%	$158.5279	$158.53	$158.55	$158.50
Purchase #7	$212.25	13.602%	$241.1202	$241.12	$241.10	$241.10
7 purchase totals =	$929.88		$1,030.2810	$1,030.29	$1,030.30	$1,030.20