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	$238.25	4.838%	$249.7765	$249.78	$249.80	$249.80
Purchase #2	$55.28	7.296%	$59.3132	$59.31	$59.30	$59.30
Purchase #3	$33.28	7.178%	$35.6688	$35.67	$35.65	$35.70
Purchase #4	$229.42	6.606%	$244.5755	$244.58	$244.60	$244.60
Purchase #5	$248.41	5.540%	$262.1719	$262.17	$262.15	$262.20
Purchase #6	$16.41	12.763%	$18.5044	$18.50	$18.50	$18.50
Purchase #7	$206.85	4.501%	$216.1603	$216.16	$216.15	$216.20
7 purchase totals =	$1,027.90		$1,086.1706	$1,086.17	$1,086.15	$1,086.30