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	$182.89	9.866%	$200.9339	$200.93	$200.95	$200.90
Purchase #2	$121.74	11.391%	$135.6074	$135.61	$135.60	$135.60
Purchase #3	$239.78	10.137%	$264.0865	$264.09	$264.10	$264.10
Purchase #4	$127.90	9.342%	$139.8484	$139.85	$139.85	$139.80
Purchase #5	$35.44	12.152%	$39.7467	$39.75	$39.75	$39.70
Purchase #6	$139.88	8.276%	$151.4565	$151.46	$151.45	$151.50
Purchase #7	$19.68	11.243%	$21.8926	$21.89	$21.90	$21.90
7 purchase totals =	$867.31		$953.5720	$953.58	$953.60	$953.50