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	$239.53	5.736%	$253.2694	$253.27	$253.25	$253.30
Purchase #2	$220.80	10.782%	$244.6067	$244.61	$244.60	$244.60
Purchase #3	$180.89	5.430%	$190.7123	$190.71	$190.70	$190.70
Purchase #4	$40.51	4.648%	$42.3929	$42.39	$42.40	$42.40
Purchase #5	$164.36	13.669%	$186.8264	$186.83	$186.85	$186.80
Purchase #6	$169.78	10.481%	$187.5746	$187.57	$187.55	$187.60
Purchase #7	$77.73	12.105%	$87.1392	$87.14	$87.15	$87.10
7 purchase totals =	$1,093.60		$1,192.5215	$1,192.52	$1,192.50	$1,192.50