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	$13.73	8.784%	$14.936	$14.94	$14.95	$14.90
Purchase #2	$20.49	4.629%	$21.4385	$21.44	$21.45	$21.40
Purchase #3	$170.39	11.516%	$190.0121	$190.01	$190.00	$190.00
Purchase #4	$224.95	3.528%	$232.8862	$232.89	$232.90	$232.90
Purchase #5	$56.81	5.384%	$59.8687	$59.87	$59.85	$59.90
Purchase #6	$32.85	7.256%	$35.2336	$35.23	$35.25	$35.20
Purchase #7	$151.53	4.507%	$158.3595	$158.36	$158.35	$158.40
7 purchase totals =	$670.75		$712.7346	$712.74	$712.75	$712.70