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	$133.35	13.259%	$151.0309	$151.03	$151.05	$151.00
Purchase #2	$33.33	11.104%	$37.031	$37.03	$37.05	$37.00
Purchase #3	$65.70	10.276%	$72.4513	$72.45	$72.45	$72.50
Purchase #4	$112.50	4.789%	$117.8876	$117.89	$117.90	$117.90
Purchase #5	$115.82	7.379%	$124.3664	$124.37	$124.35	$124.40
Purchase #6	$129.79	7.321%	$139.2919	$139.29	$139.30	$139.30
Purchase #7	$125.46	11.843%	$140.3182	$140.32	$140.30	$140.30
7 purchase totals =	$715.95		$782.3773	$782.38	$782.40	$782.40