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	$85.59	12.488%	$96.2785	$96.28	$96.30	$96.30
Purchase #2	$31.94	11.454%	$35.5984	$35.60	$35.60	$35.60
Purchase #3	$21.37	6.590%	$22.7783	$22.78	$22.80	$22.80
Purchase #4	$46.74	5.823%	$49.4617	$49.46	$49.45	$49.50
Purchase #5	$158.54	4.531%	$165.7234	$165.72	$165.70	$165.70
Purchase #6	$12.68	6.562%	$13.5121	$13.51	$13.50	$13.50
Purchase #7	$133.46	12.866%	$150.631	$150.63	$150.65	$150.60
7 purchase totals =	$490.32		$533.9834	$533.98	$534.00	$534.00