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	$234.50	9.274%	$256.2475	$256.25	$256.25	$256.20
Purchase #2	$226.40	13.323%	$256.5633	$256.56	$256.55	$256.60
Purchase #3	$29.39	4.672%	$30.7631	$30.76	$30.75	$30.80
Purchase #4	$120.35	6.158%	$127.7612	$127.76	$127.75	$127.80
Purchase #5	$24.37	6.160%	$25.8712	$25.87	$25.85	$25.90
Purchase #6	$155.43	8.393%	$168.4752	$168.48	$168.50	$168.50
Purchase #7	$165.56	4.429%	$172.8927	$172.89	$172.90	$172.90
7 purchase totals =	$956.00		$1,038.5742	$1,038.57	$1,038.55	$1,038.70