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	$160.71	3.807%	$166.8282	$166.83	$166.85	$166.80
Purchase #2	$63.44	4.143%	$66.0683	$66.07	$66.05	$66.10
Purchase #3	$22.78	13.503%	$25.856	$25.86	$25.85	$25.90
Purchase #4	$222.84	13.484%	$252.8877	$252.89	$252.90	$252.90
Purchase #5	$77.31	10.361%	$85.3201	$85.32	$85.30	$85.30
Purchase #6	$144.27	12.784%	$162.7135	$162.71	$162.70	$162.70
Purchase #7	$60.93	5.624%	$64.3567	$64.36	$64.35	$64.40
7 purchase totals =	$752.28		$824.0305	$824.04	$824.00	$824.10