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	$202.52	12.133%	$227.0918	$227.09	$227.10	$227.10
Purchase #2	$50.29	7.870%	$54.2478	$54.25	$54.25	$54.20
Purchase #3	$56.93	7.761%	$61.3483	$61.35	$61.35	$61.30
Purchase #4	$235.63	5.129%	$247.7155	$247.72	$247.70	$247.70
Purchase #5	$132.27	13.639%	$150.3103	$150.31	$150.30	$150.30
Purchase #6	$47.73	5.583%	$50.3948	$50.39	$50.40	$50.40
Purchase #7	$32.78	5.507%	$34.5852	$34.59	$34.60	$34.60
7 purchase totals =	$758.15		$825.6937	$825.70	$825.70	$825.60