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	$204.90	11.509%	$228.4819	$228.48	$228.50	$228.50
Purchase #2	$41.59	3.665%	$43.1143	$43.11	$43.10	$43.10
Purchase #3	$6.49	12.340%	$7.2909	$7.29	$7.30	$7.30
Purchase #4	$65.98	8.504%	$71.5909	$71.59	$71.60	$71.60
Purchase #5	$191.82	13.528%	$217.7694	$217.77	$217.75	$217.80
Purchase #6	$176.52	5.737%	$186.647	$186.65	$186.65	$186.60
Purchase #7	$147.74	11.701%	$165.0271	$165.03	$165.05	$165.00
7 purchase totals =	$835.04		$919.9215	$919.92	$919.95	$919.90