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	$221.72	10.743%	$245.5394	$245.54	$245.55	$245.50
Purchase #2	$210.48	5.635%	$222.3405	$222.34	$222.35	$222.30
Purchase #3	$235.54	9.659%	$258.2908	$258.29	$258.30	$258.30
Purchase #4	$162.33	5.549%	$171.3377	$171.34	$171.35	$171.30
Purchase #5	$66.76	8.733%	$72.5902	$72.59	$72.60	$72.60
Purchase #6	$77.37	13.365%	$87.7105	$87.71	$87.70	$87.70
Purchase #7	$136.49	7.732%	$147.0434	$147.04	$147.05	$147.00
7 purchase totals =	$1,110.69		$1,204.8525	$1,204.85	$1,204.90	$1,204.70