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	$220.77	9.376%	$241.4694	$241.47	$241.45	$241.50
Purchase #2	$197.70	6.445%	$210.4418	$210.44	$210.45	$210.40
Purchase #3	$34.78	13.338%	$39.419	$39.42	$39.40	$39.40
Purchase #4	$128.29	12.630%	$144.493	$144.49	$144.50	$144.50
Purchase #5	$6.74	6.373%	$7.1695	$7.17	$7.15	$7.20
Purchase #6	$79.49	13.684%	$90.3674	$90.37	$90.35	$90.40
Purchase #7	$18.66	8.609%	$20.2664	$20.27	$20.25	$20.30
7 purchase totals =	$686.43		$753.6265	$753.63	$753.55	$753.70