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	$33.61	10.554%	$37.1572	$37.16	$37.15	$37.20
Purchase #2	$57.83	11.499%	$64.4799	$64.48	$64.50	$64.50
Purchase #3	$241.65	4.198%	$251.7945	$251.79	$251.80	$251.80
Purchase #4	$213.27	11.835%	$238.5105	$238.51	$238.50	$238.50
Purchase #5	$237.34	9.826%	$260.661	$260.66	$260.65	$260.70
Purchase #6	$227.88	11.180%	$253.357	$253.36	$253.35	$253.40
Purchase #7	$193.42	3.843%	$200.8531	$200.85	$200.85	$200.90
7 purchase totals =	$1,205.00		$1,306.8132	$1,306.81	$1,306.80	$1,307.00