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	$145.77	4.169%	$151.8472	$151.85	$151.85	$151.80
Purchase #2	$246.51	11.316%	$274.4051	$274.41	$274.40	$274.40
Purchase #3	$18.71	5.788%	$19.7929	$19.79	$19.80	$19.80
Purchase #4	$175.44	8.492%	$190.3384	$190.34	$190.35	$190.30
Purchase #5	$180.31	8.812%	$196.1989	$196.20	$196.20	$196.20
Purchase #6	$64.27	10.702%	$71.1482	$71.15	$71.15	$71.10
Purchase #7	$62.45	5.669%	$65.9903	$65.99	$66.00	$66.00
7 purchase totals =	$893.46		$969.7210	$969.73	$969.75	$969.60