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	$120.76	8.303%	$130.7867	$130.79	$130.80	$130.80
Purchase #2	$99.73	11.561%	$111.2598	$111.26	$111.25	$111.30
Purchase #3	$73.38	11.129%	$81.5465	$81.55	$81.55	$81.50
Purchase #4	$52.86	7.121%	$56.6242	$56.62	$56.60	$56.60
Purchase #5	$94.70	11.542%	$105.6303	$105.63	$105.65	$105.60
Purchase #6	$209.81	5.461%	$221.2677	$221.27	$221.25	$221.30
Purchase #7	$60.59	8.124%	$65.5123	$65.51	$65.50	$65.50
7 purchase totals =	$711.83		$772.6275	$772.63	$772.60	$772.60