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	$125.48	11.432%	$139.8249	$139.82	$139.80	$139.80
Purchase #2	$18.56	11.752%	$20.7412	$20.74	$20.75	$20.70
Purchase #3	$96.48	3.474%	$99.8317	$99.83	$99.85	$99.80
Purchase #4	$139.42	11.720%	$155.76	$155.76	$155.75	$155.80
Purchase #5	$21.74	9.797%	$23.8699	$23.87	$23.85	$23.90
Purchase #6	$132.70	13.191%	$150.2045	$150.20	$150.20	$150.20
Purchase #7	$33.47	10.664%	$37.0392	$37.04	$37.05	$37.00
7 purchase totals =	$567.85		$627.2714	$627.26	$627.25	$627.20