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	$119.58	9.680%	$131.1553	$131.16	$131.15	$131.20
Purchase #2	$11.85	4.128%	$12.3392	$12.34	$12.35	$12.30
Purchase #3	$40.90	7.166%	$43.8309	$43.83	$43.85	$43.80
Purchase #4	$202.88	12.128%	$227.4853	$227.49	$227.50	$227.50
Purchase #5	$6.36	10.710%	$7.0412	$7.04	$7.05	$7.00
Purchase #6	$33.47	5.280%	$35.2372	$35.24	$35.25	$35.20
Purchase #7	$204.91	10.134%	$225.6756	$225.68	$225.70	$225.70
7 purchase totals =	$619.95		$682.7647	$682.78	$682.85	$682.70