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	$172.74	13.633%	$196.2896	$196.29	$196.30	$196.30
Purchase #2	$49.81	11.407%	$55.4918	$55.49	$55.50	$55.50
Purchase #3	$36.25	10.860%	$40.1868	$40.19	$40.20	$40.20
Purchase #4	$222.46	10.344%	$245.4713	$245.47	$245.45	$245.50
Purchase #5	$62.41	12.127%	$69.9785	$69.98	$70.00	$70.00
Purchase #6	$78.82	10.548%	$87.1339	$87.13	$87.15	$87.10
Purchase #7	$219.72	8.714%	$238.8664	$238.87	$238.85	$238.90
7 purchase totals =	$842.21		$933.4183	$933.42	$933.45	$933.50