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	$20.46	13.778%	$23.279	$23.28	$23.30	$23.30
Purchase #2	$66.76	13.285%	$75.6291	$75.63	$75.65	$75.60
Purchase #3	$107.45	11.605%	$119.9196	$119.92	$119.90	$119.90
Purchase #4	$62.31	5.600%	$65.7994	$65.80	$65.80	$65.80
Purchase #5	$104.29	13.256%	$118.1147	$118.11	$118.10	$118.10
Purchase #6	$69.30	4.459%	$72.3901	$72.39	$72.40	$72.40
Purchase #7	$32.70	8.425%	$35.455	$35.46	$35.45	$35.50
7 purchase totals =	$463.27		$510.5869	$510.59	$510.60	$510.60