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	$13.62	9.590%	$14.9262	$14.93	$14.95	$14.90
Purchase #2	$211.90	5.137%	$222.7853	$222.79	$222.80	$222.80
Purchase #3	$20.38	4.656%	$21.3289	$21.33	$21.35	$21.30
Purchase #4	$93.63	10.525%	$103.4846	$103.48	$103.50	$103.50
Purchase #5	$132.32	11.438%	$147.4548	$147.45	$147.45	$147.50
Purchase #6	$243.93	11.722%	$272.5235	$272.52	$272.50	$272.50
Purchase #7	$137.46	6.656%	$146.6093	$146.61	$146.60	$146.60
7 purchase totals =	$853.24		$929.1126	$929.11	$929.15	$929.10