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	$41.68	9.610%	$45.6854	$45.69	$45.70	$45.70
Purchase #2	$207.85	12.143%	$233.0892	$233.09	$233.10	$233.10
Purchase #3	$94.61	4.764%	$99.1172	$99.12	$99.10	$99.10
Purchase #4	$145.39	7.389%	$156.1329	$156.13	$156.15	$156.10
Purchase #5	$168.90	6.588%	$180.0271	$180.03	$180.05	$180.00
Purchase #6	$59.88	5.790%	$63.3471	$63.35	$63.35	$63.30
Purchase #7	$214.98	12.337%	$241.5021	$241.50	$241.50	$241.50
7 purchase totals =	$933.29		$1,018.9010	$1,018.91	$1,018.95	$1,018.80