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	$188.63	13.105%	$213.35	$213.35	$213.35	$213.40
Purchase #2	$74.62	5.145%	$78.4592	$78.46	$78.45	$78.50
Purchase #3	$246.48	13.387%	$279.4763	$279.48	$279.50	$279.50
Purchase #4	$13.30	4.186%	$13.8567	$13.86	$13.85	$13.90
Purchase #5	$13.76	4.824%	$14.4238	$14.42	$14.40	$14.40
Purchase #6	$135.80	5.648%	$143.47	$143.47	$143.45	$143.50
Purchase #7	$229.62	4.206%	$239.2778	$239.28	$239.30	$239.30
7 purchase totals =	$902.21		$982.3138	$982.32	$982.30	$982.50