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	$135.61	9.151%	$148.0197	$148.02	$148.00	$148.00
Purchase #2	$12.60	4.634%	$13.1839	$13.18	$13.20	$13.20
Purchase #3	$133.86	7.185%	$143.4778	$143.48	$143.50	$143.50
Purchase #4	$246.58	5.368%	$259.8164	$259.82	$259.80	$259.80
Purchase #5	$37.57	7.461%	$40.3731	$40.37	$40.35	$40.40
Purchase #6	$217.98	7.407%	$234.1258	$234.13	$234.15	$234.10
Purchase #7	$148.78	13.203%	$168.4234	$168.42	$168.40	$168.40
7 purchase totals =	$932.98		$1,007.4201	$1,007.42	$1,007.40	$1,007.40