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	$121.57	4.769%	$127.3677	$127.37	$127.35	$127.40
Purchase #2	$55.29	5.718%	$58.4515	$58.45	$58.45	$58.50
Purchase #3	$66.41	10.845%	$73.6122	$73.61	$73.60	$73.60
Purchase #4	$213.53	6.341%	$227.0699	$227.07	$227.05	$227.10
Purchase #5	$71.47	7.831%	$77.0668	$77.07	$77.05	$77.10
Purchase #6	$81.59	4.637%	$85.3733	$85.37	$85.35	$85.40
Purchase #7	$85.83	10.262%	$94.6379	$94.64	$94.65	$94.60
7 purchase totals =	$695.69		$743.5793	$743.58	$743.50	$743.70