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	$191.79	13.675%	$218.0173	$218.02	$218.00	$218.00
Purchase #2	$32.72	9.523%	$35.8359	$35.84	$35.85	$35.80
Purchase #3	$45.57	3.337%	$47.0907	$47.09	$47.10	$47.10
Purchase #4	$52.60	7.589%	$56.5918	$56.59	$56.60	$56.60
Purchase #5	$48.67	9.576%	$53.3306	$53.33	$53.35	$53.30
Purchase #6	$31.73	10.586%	$35.0889	$35.09	$35.10	$35.10
Purchase #7	$151.38	11.318%	$168.5132	$168.51	$168.50	$168.50
7 purchase totals =	$554.46		$614.4684	$614.47	$614.50	$614.40