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	$41.38	9.833%	$45.4489	$45.45	$45.45	$45.40
Purchase #2	$216.94	12.831%	$244.7756	$244.78	$244.80	$244.80
Purchase #3	$177.77	6.341%	$189.0424	$189.04	$189.05	$189.00
Purchase #4	$238.74	7.185%	$255.8935	$255.89	$255.90	$255.90
Purchase #5	$201.40	11.752%	$225.0685	$225.07	$225.05	$225.10
Purchase #6	$156.65	3.729%	$162.4915	$162.49	$162.50	$162.50
Purchase #7	$194.75	12.103%	$218.3206	$218.32	$218.30	$218.30
7 purchase totals =	$1,227.63		$1,341.0410	$1,341.04	$1,341.05	$1,341.00