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	$37.92	11.464%	$42.2671	$42.27	$42.25	$42.30
Purchase #2	$90.25	13.589%	$102.5141	$102.51	$102.50	$102.50
Purchase #3	$31.65	5.392%	$33.3566	$33.36	$33.35	$33.40
Purchase #4	$64.64	10.109%	$71.1745	$71.17	$71.15	$71.20
Purchase #5	$216.65	13.808%	$246.565	$246.57	$246.55	$246.60
Purchase #6	$23.51	10.643%	$26.0122	$26.01	$26.00	$26.00
Purchase #7	$166.68	8.346%	$180.5911	$180.59	$180.60	$180.60
7 purchase totals =	$631.30		$702.4806	$702.48	$702.40	$702.60