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	$111.57	6.176%	$118.4606	$118.46	$118.45	$118.50
Purchase #2	$140.93	7.865%	$152.0141	$152.01	$152.00	$152.00
Purchase #3	$239.39	11.292%	$266.4219	$266.42	$266.40	$266.40
Purchase #4	$240.79	3.622%	$249.5114	$249.51	$249.50	$249.50
Purchase #5	$227.31	3.140%	$234.4475	$234.45	$234.45	$234.40
Purchase #6	$54.54	9.767%	$59.8669	$59.87	$59.85	$59.90
Purchase #7	$6.64	5.733%	$7.0207	$7.02	$7.00	$7.00
7 purchase totals =	$1,021.17		$1,087.7431	$1,087.74	$1,087.65	$1,087.70