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	$196.37	10.588%	$217.1617	$217.16	$217.15	$217.20
Purchase #2	$131.60	7.801%	$141.8661	$141.87	$141.85	$141.90
Purchase #3	$154.53	13.356%	$175.169	$175.17	$175.15	$175.20
Purchase #4	$77.45	10.518%	$85.5962	$85.60	$85.60	$85.60
Purchase #5	$9.60	11.417%	$10.696	$10.70	$10.70	$10.70
Purchase #6	$46.94	6.611%	$50.0432	$50.04	$50.05	$50.00
Purchase #7	$134.84	12.292%	$151.4145	$151.41	$151.40	$151.40
7 purchase totals =	$751.33		$831.9467	$831.95	$831.90	$832.00