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	$60.59	9.635%	$66.4278	$66.43	$66.45	$66.40
Purchase #2	$222.69	4.662%	$233.0718	$233.07	$233.05	$233.10
Purchase #3	$137.70	9.270%	$150.4648	$150.46	$150.45	$150.50
Purchase #4	$65.90	9.248%	$71.9944	$71.99	$72.00	$72.00
Purchase #5	$85.34	12.157%	$95.7148	$95.71	$95.70	$95.70
Purchase #6	$64.38	5.162%	$67.7033	$67.70	$67.70	$67.70
Purchase #7	$69.54	8.618%	$75.533	$75.53	$75.55	$75.50
7 purchase totals =	$706.14		$760.9099	$760.89	$760.90	$760.90