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	$91.65	4.253%	$95.5479	$95.55	$95.55	$95.50
Purchase #2	$152.80	7.714%	$164.587	$164.59	$164.60	$164.60
Purchase #3	$125.78	12.621%	$141.6547	$141.65	$141.65	$141.70
Purchase #4	$136.59	6.333%	$145.2402	$145.24	$145.25	$145.20
Purchase #5	$123.72	13.233%	$140.0919	$140.09	$140.10	$140.10
Purchase #6	$55.37	11.236%	$61.5914	$61.59	$61.60	$61.60
Purchase #7	$179.43	9.130%	$195.812	$195.81	$195.80	$195.80
7 purchase totals =	$865.34		$944.5251	$944.52	$944.55	$944.50