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	$50.53	4.734%	$52.9221	$52.92	$52.90	$52.90
Purchase #2	$93.62	11.228%	$104.1317	$104.13	$104.15	$104.10
Purchase #3	$12.38	9.176%	$13.516	$13.52	$13.50	$13.50
Purchase #4	$28.85	10.857%	$31.9822	$31.98	$32.00	$32.00
Purchase #5	$166.62	13.762%	$189.5502	$189.55	$189.55	$189.60
Purchase #6	$65.43	4.105%	$68.1159	$68.12	$68.10	$68.10
Purchase #7	$135.85	4.282%	$141.6671	$141.67	$141.65	$141.70
7 purchase totals =	$553.28		$601.8852	$601.89	$601.85	$601.90