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	$10.32	11.831%	$11.541	$11.54	$11.55	$11.50
Purchase #2	$205.57	4.189%	$214.1813	$214.18	$214.20	$214.20
Purchase #3	$30.70	9.590%	$33.6441	$33.64	$33.65	$33.60
Purchase #4	$248.96	10.817%	$275.89	$275.89	$275.90	$275.90
Purchase #5	$35.49	4.398%	$37.0509	$37.05	$37.05	$37.10
Purchase #6	$73.99	13.221%	$83.7722	$83.77	$83.75	$83.80
Purchase #7	$48.60	5.417%	$51.2327	$51.23	$51.25	$51.20
7 purchase totals =	$653.63		$707.3122	$707.30	$707.35	$707.30