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	$128.40	3.729%	$133.188	$133.19	$133.20	$133.20
Purchase #2	$71.28	8.568%	$77.3873	$77.39	$77.40	$77.40
Purchase #3	$233.37	12.553%	$262.6649	$262.66	$262.65	$262.70
Purchase #4	$248.89	4.820%	$260.8865	$260.89	$260.90	$260.90
Purchase #5	$238.46	7.713%	$256.8524	$256.85	$256.85	$256.90
Purchase #6	$152.78	8.390%	$165.5982	$165.60	$165.60	$165.60
Purchase #7	$149.60	11.204%	$166.3612	$166.36	$166.35	$166.40
7 purchase totals =	$1,222.78		$1,322.9385	$1,322.94	$1,322.95	$1,323.10