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	$79.45	4.255%	$82.8306	$82.83	$82.85	$82.80
Purchase #2	$115.39	13.832%	$131.3507	$131.35	$131.35	$131.40
Purchase #3	$154.89	13.167%	$175.2844	$175.28	$175.30	$175.30
Purchase #4	$10.58	10.124%	$11.6511	$11.65	$11.65	$11.70
Purchase #5	$48.95	7.624%	$52.6819	$52.68	$52.70	$52.70
Purchase #6	$59.64	3.184%	$61.5389	$61.54	$61.55	$61.50
Purchase #7	$47.77	6.299%	$50.779	$50.78	$50.80	$50.80
7 purchase totals =	$516.67		$566.1166	$566.11	$566.20	$566.20