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	$54.56	7.601%	$58.7071	$58.71	$58.70	$58.70
Purchase #2	$83.69	4.179%	$87.1874	$87.19	$87.20	$87.20
Purchase #3	$67.82	4.247%	$70.7003	$70.70	$70.70	$70.70
Purchase #4	$198.82	9.381%	$217.4713	$217.47	$217.45	$217.50
Purchase #5	$36.67	11.548%	$40.9047	$40.90	$40.90	$40.90
Purchase #6	$78.96	8.222%	$85.4521	$85.45	$85.45	$85.50
Purchase #7	$232.77	3.194%	$240.2047	$240.20	$240.20	$240.20
7 purchase totals =	$753.29		$800.6276	$800.62	$800.60	$800.70