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	$232.63	7.406%	$249.8586	$249.86	$249.85	$249.90
Purchase #2	$151.25	11.287%	$168.3216	$168.32	$168.30	$168.30
Purchase #3	$77.89	3.466%	$80.5897	$80.59	$80.60	$80.60
Purchase #4	$201.94	13.839%	$229.8865	$229.89	$229.90	$229.90
Purchase #5	$99.66	13.608%	$113.2217	$113.22	$113.20	$113.20
Purchase #6	$49.50	10.193%	$54.5455	$54.55	$54.55	$54.50
Purchase #7	$195.29	10.741%	$216.2661	$216.27	$216.25	$216.30
7 purchase totals =	$1,008.16		$1,112.6897	$1,112.70	$1,112.65	$1,112.70