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	$102.89	13.766%	$117.0538	$117.05	$117.05	$117.10
Purchase #2	$76.54	5.545%	$80.7841	$80.78	$80.80	$80.80
Purchase #3	$222.26	8.222%	$240.5342	$240.53	$240.55	$240.50
Purchase #4	$169.79	8.463%	$184.1593	$184.16	$184.15	$184.20
Purchase #5	$165.49	4.466%	$172.8808	$172.88	$172.90	$172.90
Purchase #6	$226.25	8.560%	$245.617	$245.62	$245.60	$245.60
Purchase #7	$33.30	5.603%	$35.1658	$35.17	$35.15	$35.20
7 purchase totals =	$996.52		$1,076.1950	$1,076.19	$1,076.20	$1,076.30