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	$22.58	5.644%	$23.8544	$23.85	$23.85	$23.90
Purchase #2	$20.52	3.590%	$21.2567	$21.26	$21.25	$21.30
Purchase #3	$118.25	4.165%	$123.1751	$123.18	$123.20	$123.20
Purchase #4	$214.85	12.583%	$241.8846	$241.88	$241.90	$241.90
Purchase #5	$91.34	11.170%	$101.5427	$101.54	$101.55	$101.50
Purchase #6	$29.46	10.190%	$32.462	$32.46	$32.45	$32.50
Purchase #7	$75.87	4.871%	$79.5656	$79.57	$79.55	$79.60
7 purchase totals =	$572.87		$623.7411	$623.74	$623.75	$623.90