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	$40.73	12.204%	$45.7007	$45.70	$45.70	$45.70
Purchase #2	$141.51	3.605%	$146.6114	$146.61	$146.60	$146.60
Purchase #3	$152.79	13.478%	$173.383	$173.38	$173.40	$173.40
Purchase #4	$26.65	4.540%	$27.8599	$27.86	$27.85	$27.90
Purchase #5	$245.63	12.116%	$275.3905	$275.39	$275.40	$275.40
Purchase #6	$95.64	4.612%	$100.0509	$100.05	$100.05	$100.10
Purchase #7	$163.75	13.838%	$186.4097	$186.41	$186.40	$186.40
7 purchase totals =	$866.70		$955.4061	$955.40	$955.40	$955.50