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	$101.62	10.205%	$111.9903	$111.99	$112.00	$112.00
Purchase #2	$75.27	10.675%	$83.3051	$83.31	$83.30	$83.30
Purchase #3	$60.61	10.304%	$66.8553	$66.86	$66.85	$66.90
Purchase #4	$210.81	5.675%	$222.7735	$222.77	$222.75	$222.80
Purchase #5	$154.85	11.164%	$172.1375	$172.14	$172.15	$172.10
Purchase #6	$186.77	5.618%	$197.2627	$197.26	$197.25	$197.30
Purchase #7	$137.54	8.119%	$148.7069	$148.71	$148.70	$148.70
7 purchase totals =	$927.47		$1,003.0313	$1,003.04	$1,003.00	$1,003.10