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	$38.73	12.585%	$43.6042	$43.60	$43.60	$43.60
Purchase #2	$202.41	7.278%	$217.1414	$217.14	$217.15	$217.10
Purchase #3	$128.89	13.438%	$146.2102	$146.21	$146.20	$146.20
Purchase #4	$151.31	12.666%	$170.4749	$170.47	$170.45	$170.50
Purchase #5	$73.45	13.431%	$83.3151	$83.32	$83.30	$83.30
Purchase #6	$43.56	7.196%	$46.6946	$46.69	$46.70	$46.70
Purchase #7	$156.83	12.721%	$176.7803	$176.78	$176.80	$176.80
7 purchase totals =	$795.18		$884.2207	$884.21	$884.20	$884.20