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	$88.34	7.419%	$94.8939	$94.89	$94.90	$94.90
Purchase #2	$177.79	10.664%	$196.7495	$196.75	$196.75	$196.70
Purchase #3	$108.81	13.796%	$123.8214	$123.82	$123.80	$123.80
Purchase #4	$155.95	7.711%	$167.9753	$167.98	$168.00	$168.00
Purchase #5	$188.76	10.385%	$208.3627	$208.36	$208.35	$208.40
Purchase #6	$131.34	5.476%	$138.5322	$138.53	$138.55	$138.50
Purchase #7	$28.43	12.575%	$32.0051	$32.01	$32.00	$32.00
7 purchase totals =	$879.42		$962.3401	$962.34	$962.35	$962.30