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	$241.82	13.372%	$274.1562	$274.16	$274.15	$274.20
Purchase #2	$132.59	12.861%	$149.6424	$149.64	$149.65	$149.60
Purchase #3	$95.78	6.854%	$102.3448	$102.34	$102.35	$102.30
Purchase #4	$130.28	6.275%	$138.4551	$138.46	$138.45	$138.50
Purchase #5	$59.32	6.297%	$63.0554	$63.06	$63.05	$63.10
Purchase #6	$215.27	6.275%	$228.7782	$228.78	$228.80	$228.80
Purchase #7	$82.25	3.842%	$85.41	$85.41	$85.40	$85.40
7 purchase totals =	$957.31		$1,041.8421	$1,041.85	$1,041.85	$1,041.90