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	$146.58	7.457%	$157.5105	$157.51	$157.50	$157.50
Purchase #2	$155.59	9.717%	$170.7087	$170.71	$170.70	$170.70
Purchase #3	$82.32	7.168%	$88.2207	$88.22	$88.20	$88.20
Purchase #4	$245.91	11.866%	$275.0897	$275.09	$275.10	$275.10
Purchase #5	$74.65	5.139%	$78.4863	$78.49	$78.50	$78.50
Purchase #6	$152.94	3.509%	$158.3067	$158.31	$158.30	$158.30
Purchase #7	$206.37	10.668%	$228.3856	$228.39	$228.40	$228.40
7 purchase totals =	$1,064.36		$1,156.7082	$1,156.72	$1,156.70	$1,156.70