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	$185.61	11.273%	$206.5338	$206.53	$206.55	$206.50
Purchase #2	$17.28	5.149%	$18.1697	$18.17	$18.15	$18.20
Purchase #3	$232.41	3.500%	$240.5444	$240.54	$240.55	$240.50
Purchase #4	$94.78	6.222%	$100.6772	$100.68	$100.70	$100.70
Purchase #5	$77.33	4.103%	$80.5028	$80.50	$80.50	$80.50
Purchase #6	$227.32	9.172%	$248.1698	$248.17	$248.15	$248.20
Purchase #7	$31.54	7.366%	$33.8632	$33.86	$33.85	$33.90
7 purchase totals =	$866.27		$928.4609	$928.45	$928.45	$928.50