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	$96.61	4.184%	$100.6522	$100.65	$100.65	$100.70
Purchase #2	$145.53	13.668%	$165.421	$165.42	$165.40	$165.40
Purchase #3	$209.51	4.577%	$219.0993	$219.10	$219.10	$219.10
Purchase #4	$213.70	5.217%	$224.8487	$224.85	$224.85	$224.80
Purchase #5	$48.65	7.509%	$52.3031	$52.30	$52.30	$52.30
Purchase #6	$135.61	9.659%	$148.7086	$148.71	$148.70	$148.70
Purchase #7	$42.58	7.538%	$45.7897	$45.79	$45.80	$45.80
7 purchase totals =	$892.19		$956.8226	$956.82	$956.80	$956.80