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	$215.29	10.568%	$238.0418	$238.04	$238.05	$238.00
Purchase #2	$39.54	10.361%	$43.6367	$43.64	$43.65	$43.60
Purchase #3	$215.90	11.237%	$240.1607	$240.16	$240.15	$240.20
Purchase #4	$140.55	5.778%	$148.671	$148.67	$148.65	$148.70
Purchase #5	$32.79	6.312%	$34.8597	$34.86	$34.85	$34.90
Purchase #6	$63.53	13.522%	$72.1205	$72.12	$72.10	$72.10
Purchase #7	$46.61	8.132%	$50.4003	$50.40	$50.40	$50.40
7 purchase totals =	$754.21		$827.8907	$827.89	$827.85	$827.90