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	$91.34	6.631%	$97.3968	$97.40	$97.40	$97.40
Purchase #2	$66.59	11.144%	$74.0108	$74.01	$74.00	$74.00
Purchase #3	$157.39	6.679%	$167.9021	$167.90	$167.90	$167.90
Purchase #4	$192.78	8.433%	$209.0371	$209.04	$209.05	$209.00
Purchase #5	$64.75	3.622%	$67.0952	$67.10	$67.10	$67.10
Purchase #6	$220.72	13.761%	$251.0933	$251.09	$251.10	$251.10
Purchase #7	$53.90	11.118%	$59.8926	$59.89	$59.90	$59.90
7 purchase totals =	$847.47		$926.4279	$926.43	$926.45	$926.40