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	$145.61	5.735%	$153.9607	$153.96	$153.95	$154.00
Purchase #2	$39.49	3.294%	$40.7908	$40.79	$40.80	$40.80
Purchase #3	$126.34	11.755%	$141.1913	$141.19	$141.20	$141.20
Purchase #4	$151.82	10.576%	$167.8765	$167.88	$167.90	$167.90
Purchase #5	$79.98	11.832%	$89.4432	$89.44	$89.45	$89.40
Purchase #6	$180.35	12.853%	$203.5304	$203.53	$203.55	$203.50
Purchase #7	$144.86	4.573%	$151.4844	$151.48	$151.50	$151.50
7 purchase totals =	$868.45		$948.2773	$948.27	$948.35	$948.30