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	$169.31	4.625%	$177.1406	$177.14	$177.15	$177.10
Purchase #2	$65.83	8.732%	$71.5783	$71.58	$71.60	$71.60
Purchase #3	$73.39	4.285%	$76.5348	$76.53	$76.55	$76.50
Purchase #4	$17.31	3.244%	$17.8715	$17.87	$17.85	$17.90
Purchase #5	$41.32	7.519%	$44.4269	$44.43	$44.45	$44.40
Purchase #6	$87.57	3.306%	$90.4651	$90.47	$90.45	$90.50
Purchase #7	$16.91	9.627%	$18.5379	$18.54	$18.55	$18.50
7 purchase totals =	$471.64		$496.5551	$496.56	$496.60	$496.50