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	$148.95	7.667%	$160.37	$160.37	$160.35	$160.40
Purchase #2	$199.29	5.360%	$209.9719	$209.97	$209.95	$210.00
Purchase #3	$78.42	9.132%	$85.5813	$85.58	$85.60	$85.60
Purchase #4	$90.31	11.686%	$100.8636	$100.86	$100.85	$100.90
Purchase #5	$23.86	11.178%	$26.5271	$26.53	$26.55	$26.50
Purchase #6	$207.98	9.447%	$227.6279	$227.63	$227.65	$227.60
Purchase #7	$88.56	13.610%	$100.613	$100.61	$100.60	$100.60
7 purchase totals =	$837.37		$911.5548	$911.55	$911.55	$911.60