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	$116.87	10.314%	$128.924	$128.92	$128.90	$128.90
Purchase #2	$176.74	8.577%	$191.899	$191.90	$191.90	$191.90
Purchase #3	$109.87	12.423%	$123.5192	$123.52	$123.50	$123.50
Purchase #4	$199.40	11.359%	$222.0498	$222.05	$222.05	$222.00
Purchase #5	$130.76	10.532%	$144.5316	$144.53	$144.55	$144.50
Purchase #6	$219.79	13.558%	$249.5891	$249.59	$249.60	$249.60
Purchase #7	$190.59	12.802%	$214.9893	$214.99	$215.00	$215.00
7 purchase totals =	$1,144.02		$1,275.5020	$1,275.50	$1,275.50	$1,275.40