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	$233.72	11.118%	$259.705	$259.71	$259.70	$259.70
Purchase #2	$57.79	9.377%	$63.209	$63.21	$63.20	$63.20
Purchase #3	$158.82	13.824%	$180.7753	$180.78	$180.80	$180.80
Purchase #4	$96.48	4.489%	$100.811	$100.81	$100.80	$100.80
Purchase #5	$40.77	8.330%	$44.1661	$44.17	$44.15	$44.20
Purchase #6	$142.89	5.455%	$150.6846	$150.68	$150.70	$150.70
Purchase #7	$75.99	12.516%	$85.5009	$85.50	$85.50	$85.50
7 purchase totals =	$806.46		$884.8519	$884.86	$884.85	$884.90