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	$192.46	12.642%	$216.7908	$216.79	$216.80	$216.80
Purchase #2	$37.84	13.873%	$43.0895	$43.09	$43.10	$43.10
Purchase #3	$222.98	8.237%	$241.3469	$241.35	$241.35	$241.30
Purchase #4	$7.39	6.372%	$7.8609	$7.86	$7.85	$7.90
Purchase #5	$177.77	7.510%	$191.1205	$191.12	$191.10	$191.10
Purchase #6	$243.47	11.591%	$271.6906	$271.69	$271.70	$271.70
Purchase #7	$91.26	9.134%	$99.5957	$99.60	$99.60	$99.60
7 purchase totals =	$973.17		$1,071.4949	$1,071.50	$1,071.50	$1,071.50