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	$170.32	8.185%	$184.2607	$184.26	$184.25	$184.30
Purchase #2	$18.48	4.709%	$19.3502	$19.35	$19.35	$19.40
Purchase #3	$164.33	13.106%	$185.8671	$185.87	$185.85	$185.90
Purchase #4	$244.60	4.268%	$255.0395	$255.04	$255.05	$255.00
Purchase #5	$45.43	10.434%	$50.1702	$50.17	$50.15	$50.20
Purchase #6	$183.69	10.116%	$202.2721	$202.27	$202.25	$202.30
Purchase #7	$114.41	7.572%	$123.0731	$123.07	$123.05	$123.10
7 purchase totals =	$941.26		$1,020.0329	$1,020.03	$1,019.95	$1,020.20