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	$54.57	11.503%	$60.8472	$60.85	$60.85	$60.80
Purchase #2	$33.79	12.337%	$37.9587	$37.96	$37.95	$38.00
Purchase #3	$17.63	11.294%	$19.6211	$19.62	$19.60	$19.60
Purchase #4	$33.87	7.672%	$36.4685	$36.47	$36.45	$36.50
Purchase #5	$212.72	4.727%	$222.7753	$222.78	$222.80	$222.80
Purchase #6	$67.68	7.415%	$72.6985	$72.70	$72.70	$72.70
Purchase #7	$117.46	5.158%	$123.5186	$123.52	$123.50	$123.50
7 purchase totals =	$537.72		$573.8879	$573.90	$573.85	$573.90