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	$67.88	13.857%	$77.2861	$77.29	$77.30	$77.30
Purchase #2	$156.48	10.119%	$172.3142	$172.31	$172.30	$172.30
Purchase #3	$31.73	10.700%	$35.1251	$35.13	$35.15	$35.10
Purchase #4	$177.37	9.178%	$193.649	$193.65	$193.65	$193.60
Purchase #5	$250.55	3.693%	$259.8028	$259.80	$259.80	$259.80
Purchase #6	$191.47	13.601%	$217.5118	$217.51	$217.50	$217.50
Purchase #7	$117.56	11.140%	$130.6562	$130.66	$130.65	$130.70
7 purchase totals =	$993.04		$1,086.3452	$1,086.35	$1,086.35	$1,086.30