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	$126.56	12.399%	$142.2522	$142.25	$142.25	$142.30
Purchase #2	$31.83	5.761%	$33.6637	$33.66	$33.65	$33.70
Purchase #3	$237.77	10.236%	$262.1081	$262.11	$262.10	$262.10
Purchase #4	$60.71	7.470%	$65.245	$65.25	$65.25	$65.20
Purchase #5	$166.31	5.244%	$175.0313	$175.03	$175.05	$175.00
Purchase #6	$59.39	11.779%	$66.3855	$66.39	$66.40	$66.40
Purchase #7	$201.31	5.548%	$212.4787	$212.48	$212.50	$212.50
7 purchase totals =	$883.88		$957.1645	$957.17	$957.20	$957.20