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	$113.58	4.458%	$118.6434	$118.64	$118.65	$118.60
Purchase #2	$64.51	12.506%	$72.5776	$72.58	$72.60	$72.60
Purchase #3	$87.43	3.242%	$90.2645	$90.26	$90.25	$90.30
Purchase #4	$161.97	4.638%	$169.4822	$169.48	$169.50	$169.50
Purchase #5	$127.30	8.306%	$137.8735	$137.87	$137.85	$137.90
Purchase #6	$83.80	11.773%	$93.6658	$93.67	$93.65	$93.70
Purchase #7	$9.68	10.566%	$10.7028	$10.70	$10.70	$10.70
7 purchase totals =	$648.27		$693.2098	$693.20	$693.20	$693.30