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	$185.51	13.244%	$210.0789	$210.08	$210.10	$210.10
Purchase #2	$189.88	11.598%	$211.9023	$211.90	$211.90	$211.90
Purchase #3	$164.37	7.453%	$176.6205	$176.62	$176.60	$176.60
Purchase #4	$59.77	11.457%	$66.6178	$66.62	$66.60	$66.60
Purchase #5	$94.88	10.406%	$104.7532	$104.75	$104.75	$104.80
Purchase #6	$194.76	11.217%	$216.6062	$216.61	$216.60	$216.60
Purchase #7	$250.35	11.405%	$278.9024	$278.90	$278.90	$278.90
7 purchase totals =	$1,139.52		$1,265.4813	$1,265.48	$1,265.45	$1,265.50