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	$19.48	12.163%	$21.8494	$21.85	$21.85	$21.80
Purchase #2	$30.48	13.655%	$34.642	$34.64	$34.65	$34.60
Purchase #3	$6.41	11.198%	$7.1278	$7.13	$7.15	$7.10
Purchase #4	$147.95	11.801%	$165.4096	$165.41	$165.40	$165.40
Purchase #5	$31.55	12.859%	$35.607	$35.61	$35.60	$35.60
Purchase #6	$55.54	6.253%	$59.0129	$59.01	$59.00	$59.00
Purchase #7	$11.57	4.602%	$12.1025	$12.10	$12.10	$12.10
7 purchase totals =	$302.98		$335.7512	$335.75	$335.75	$335.60