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	$66.37	9.835%	$72.8975	$72.90	$72.90	$72.90
Purchase #2	$34.80	6.272%	$36.9827	$36.98	$37.00	$37.00
Purchase #3	$9.73	3.838%	$10.1034	$10.10	$10.10	$10.10
Purchase #4	$199.84	13.801%	$227.4199	$227.42	$227.40	$227.40
Purchase #5	$188.95	4.874%	$198.1594	$198.16	$198.15	$198.20
Purchase #6	$128.43	11.820%	$143.6104	$143.61	$143.60	$143.60
Purchase #7	$248.28	3.870%	$257.8884	$257.89	$257.90	$257.90
7 purchase totals =	$876.40		$947.0617	$947.06	$947.05	$947.10