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	$132.53	7.623%	$142.6328	$142.63	$142.65	$142.60
Purchase #2	$88.94	10.386%	$98.1773	$98.18	$98.20	$98.20
Purchase #3	$9.72	8.789%	$10.5743	$10.57	$10.55	$10.60
Purchase #4	$28.63	13.699%	$32.552	$32.55	$32.55	$32.60
Purchase #5	$143.61	12.448%	$161.4866	$161.49	$161.50	$161.50
Purchase #6	$44.90	11.224%	$49.9396	$49.94	$49.95	$49.90
Purchase #7	$90.98	9.111%	$99.2692	$99.27	$99.25	$99.30
7 purchase totals =	$539.31		$594.6318	$594.63	$594.65	$594.70