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	$196.46	13.445%	$222.874	$222.87	$222.85	$222.90
Purchase #2	$127.29	11.120%	$141.4446	$141.44	$141.45	$141.40
Purchase #3	$39.37	8.451%	$42.6972	$42.70	$42.70	$42.70
Purchase #4	$93.48	11.867%	$104.5733	$104.57	$104.55	$104.60
Purchase #5	$172.54	7.528%	$185.5288	$185.53	$185.55	$185.50
Purchase #6	$146.45	3.803%	$152.0195	$152.02	$152.00	$152.00
Purchase #7	$94.78	13.563%	$107.635	$107.64	$107.65	$107.60
7 purchase totals =	$870.37		$956.7724	$956.77	$956.75	$956.70