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	$210.96	5.359%	$222.2653	$222.27	$222.25	$222.30
Purchase #2	$177.50	8.105%	$191.8864	$191.89	$191.90	$191.90
Purchase #3	$137.39	3.117%	$141.6724	$141.67	$141.65	$141.70
Purchase #4	$40.77	4.590%	$42.6413	$42.64	$42.65	$42.60
Purchase #5	$85.42	3.265%	$88.209	$88.21	$88.20	$88.20
Purchase #6	$135.77	12.852%	$153.2192	$153.22	$153.20	$153.20
Purchase #7	$164.90	3.414%	$170.5297	$170.53	$170.55	$170.50
7 purchase totals =	$952.71		$1,010.4233	$1,010.43	$1,010.40	$1,010.40