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	$198.89	4.870%	$208.5759	$208.58	$208.60	$208.60
Purchase #2	$157.89	10.622%	$174.6611	$174.66	$174.65	$174.70
Purchase #3	$75.81	10.428%	$83.7155	$83.72	$83.70	$83.70
Purchase #4	$95.91	5.495%	$101.1803	$101.18	$101.20	$101.20
Purchase #5	$117.32	6.416%	$124.8473	$124.85	$124.85	$124.80
Purchase #6	$214.59	5.117%	$225.5706	$225.57	$225.55	$225.60
Purchase #7	$198.82	12.618%	$223.9071	$223.91	$223.90	$223.90
7 purchase totals =	$1,059.23		$1,142.4578	$1,142.47	$1,142.45	$1,142.50