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	$245.45	4.649%	$256.861	$256.86	$256.85	$256.90
Purchase #2	$223.57	7.854%	$241.1292	$241.13	$241.15	$241.10
Purchase #3	$158.45	8.484%	$171.8929	$171.89	$171.90	$171.90
Purchase #4	$202.58	11.381%	$225.6356	$225.64	$225.65	$225.60
Purchase #5	$238.88	5.724%	$252.5535	$252.55	$252.55	$252.60
Purchase #6	$246.50	7.440%	$264.8396	$264.84	$264.85	$264.80
Purchase #7	$85.71	10.230%	$94.4781	$94.48	$94.50	$94.50
7 purchase totals =	$1,401.14		$1,507.3899	$1,507.39	$1,507.45	$1,507.40