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	$218.92	6.330%	$232.7776	$232.78	$232.80	$232.80
Purchase #2	$195.50	13.110%	$221.1301	$221.13	$221.15	$221.10
Purchase #3	$77.81	13.853%	$88.589	$88.59	$88.60	$88.60
Purchase #4	$151.44	11.258%	$168.4891	$168.49	$168.50	$168.50
Purchase #5	$74.98	13.698%	$85.2508	$85.25	$85.25	$85.30
Purchase #6	$83.46	11.356%	$92.9377	$92.94	$92.95	$92.90
Purchase #7	$32.58	7.555%	$35.0414	$35.04	$35.05	$35.00
7 purchase totals =	$834.69		$924.2157	$924.22	$924.30	$924.20