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	$249.76	6.373%	$265.6772	$265.68	$265.70	$265.70
Purchase #2	$93.93	6.635%	$100.1623	$100.16	$100.15	$100.20
Purchase #3	$174.35	6.400%	$185.5084	$185.51	$185.50	$185.50
Purchase #4	$33.67	5.347%	$35.4703	$35.47	$35.45	$35.50
Purchase #5	$140.53	4.231%	$146.4758	$146.48	$146.50	$146.50
Purchase #6	$237.59	7.400%	$255.1717	$255.17	$255.15	$255.20
Purchase #7	$154.51	7.555%	$166.1832	$166.18	$166.20	$166.20
7 purchase totals =	$1,084.34		$1,154.6489	$1,154.65	$1,154.65	$1,154.80