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	$246.79	11.152%	$274.312	$274.31	$274.30	$274.30
Purchase #2	$35.83	13.535%	$40.6796	$40.68	$40.70	$40.70
Purchase #3	$50.85	12.426%	$57.1686	$57.17	$57.15	$57.20
Purchase #4	$183.34	4.593%	$191.7608	$191.76	$191.75	$191.80
Purchase #5	$62.50	11.344%	$69.59	$69.59	$69.60	$69.60
Purchase #6	$9.95	10.296%	$10.9745	$10.97	$10.95	$11.00
Purchase #7	$59.50	5.408%	$62.7178	$62.72	$62.70	$62.70
7 purchase totals =	$648.76		$707.2033	$707.20	$707.15	$707.30