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	$224.91	12.746%	$253.577	$253.58	$253.60	$253.60
Purchase #2	$98.82	12.545%	$111.217	$111.22	$111.20	$111.20
Purchase #3	$59.69	6.211%	$63.3973	$63.40	$63.40	$63.40
Purchase #4	$195.95	10.526%	$216.5757	$216.58	$216.60	$216.60
Purchase #5	$137.59	10.429%	$151.9393	$151.94	$151.95	$151.90
Purchase #6	$88.80	6.866%	$94.897	$94.90	$94.90	$94.90
Purchase #7	$41.82	11.746%	$46.7322	$46.73	$46.75	$46.70
7 purchase totals =	$847.58		$938.3355	$938.35	$938.40	$938.30