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	$165.86	4.419%	$173.1894	$173.19	$173.20	$173.20
Purchase #2	$144.27	10.660%	$159.6492	$159.65	$159.65	$159.60
Purchase #3	$31.48	7.321%	$33.7847	$33.78	$33.80	$33.80
Purchase #4	$52.48	12.317%	$58.944	$58.94	$58.95	$58.90
Purchase #5	$77.38	10.466%	$85.4786	$85.48	$85.50	$85.50
Purchase #6	$132.26	4.257%	$137.8903	$137.89	$137.90	$137.90
Purchase #7	$53.71	13.631%	$61.0312	$61.03	$61.05	$61.00
7 purchase totals =	$657.44		$709.9674	$709.96	$710.05	$709.90