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	$48.82	4.346%	$50.9417	$50.94	$50.95	$50.90
Purchase #2	$211.56	4.680%	$221.461	$221.46	$221.45	$221.50
Purchase #3	$239.61	10.598%	$265.0039	$265.00	$265.00	$265.00
Purchase #4	$120.49	10.568%	$133.2234	$133.22	$133.20	$133.20
Purchase #5	$42.82	12.824%	$48.3112	$48.31	$48.30	$48.30
Purchase #6	$107.47	10.810%	$119.0875	$119.09	$119.10	$119.10
Purchase #7	$170.55	11.711%	$190.5231	$190.52	$190.50	$190.50
7 purchase totals =	$941.32		$1,028.5518	$1,028.54	$1,028.50	$1,028.50