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	$243.81	7.667%	$262.5029	$262.50	$262.50	$262.50
Purchase #2	$132.60	11.756%	$148.1885	$148.19	$148.20	$148.20
Purchase #3	$209.56	4.865%	$219.7551	$219.76	$219.75	$219.80
Purchase #4	$118.78	10.112%	$130.791	$130.79	$130.80	$130.80
Purchase #5	$197.66	12.285%	$221.9425	$221.94	$221.95	$221.90
Purchase #6	$39.67	8.700%	$43.1213	$43.12	$43.10	$43.10
Purchase #7	$100.82	12.351%	$113.2723	$113.27	$113.25	$113.30
7 purchase totals =	$1,042.90		$1,139.5736	$1,139.57	$1,139.55	$1,139.60