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	$109.45	6.237%	$116.2764	$116.28	$116.30	$116.30
Purchase #2	$31.82	11.376%	$35.4398	$35.44	$35.45	$35.40
Purchase #3	$167.50	5.168%	$176.1564	$176.16	$176.15	$176.20
Purchase #4	$78.57	4.122%	$81.8087	$81.81	$81.80	$81.80
Purchase #5	$200.71	4.134%	$209.0074	$209.01	$209.00	$209.00
Purchase #6	$67.95	5.817%	$71.9027	$71.90	$71.90	$71.90
Purchase #7	$239.90	10.226%	$264.4322	$264.43	$264.45	$264.40
7 purchase totals =	$895.90		$955.0236	$955.03	$955.05	$955.00