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	$63.63	13.834%	$72.4326	$72.43	$72.45	$72.40
Purchase #2	$29.82	11.331%	$33.1989	$33.20	$33.20	$33.20
Purchase #3	$244.71	5.392%	$257.9048	$257.90	$257.90	$257.90
Purchase #4	$33.61	10.338%	$37.0846	$37.08	$37.10	$37.10
Purchase #5	$244.96	8.142%	$264.9046	$264.90	$264.90	$264.90
Purchase #6	$20.69	5.631%	$21.8551	$21.86	$21.85	$21.90
Purchase #7	$49.48	6.197%	$52.5463	$52.55	$52.55	$52.50
7 purchase totals =	$686.90		$739.9269	$739.92	$739.95	$739.90