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	$245.46	3.402%	$253.8105	$253.81	$253.80	$253.80
Purchase #2	$52.87	13.408%	$59.9588	$59.96	$59.95	$60.00
Purchase #3	$217.95	7.512%	$234.3224	$234.32	$234.30	$234.30
Purchase #4	$32.92	13.861%	$37.483	$37.48	$37.50	$37.50
Purchase #5	$210.70	4.143%	$219.4293	$219.43	$219.45	$219.40
Purchase #6	$60.53	10.228%	$66.721	$66.72	$66.70	$66.70
Purchase #7	$250.76	6.668%	$267.4807	$267.48	$267.50	$267.50
7 purchase totals =	$1,071.19		$1,139.2057	$1,139.20	$1,139.20	$1,139.20