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	$219.30	5.757%	$231.9251	$231.93	$231.95	$231.90
Purchase #2	$83.50	7.512%	$89.7725	$89.77	$89.75	$89.80
Purchase #3	$50.86	11.173%	$56.5426	$56.54	$56.55	$56.50
Purchase #4	$132.90	10.148%	$146.3867	$146.39	$146.40	$146.40
Purchase #5	$166.47	10.766%	$184.3922	$184.39	$184.40	$184.40
Purchase #6	$55.91	12.746%	$63.0363	$63.04	$63.05	$63.00
Purchase #7	$74.25	8.864%	$80.8315	$80.83	$80.85	$80.80
7 purchase totals =	$783.19		$852.8869	$852.89	$852.95	$852.80