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	$136.52	10.216%	$150.4669	$150.47	$150.45	$150.50
Purchase #2	$7.51	12.545%	$8.4521	$8.45	$8.45	$8.50
Purchase #3	$83.89	6.339%	$89.2078	$89.21	$89.20	$89.20
Purchase #4	$92.65	6.320%	$98.5055	$98.51	$98.50	$98.50
Purchase #5	$208.60	5.815%	$220.7301	$220.73	$220.75	$220.70
Purchase #6	$24.66	12.519%	$27.7472	$27.75	$27.75	$27.70
Purchase #7	$70.78	3.318%	$73.1285	$73.13	$73.15	$73.10
7 purchase totals =	$624.61		$668.2381	$668.25	$668.25	$668.20