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	$114.26	5.745%	$120.8242	$120.82	$120.80	$120.80
Purchase #2	$132.62	4.508%	$138.5985	$138.60	$138.60	$138.60
Purchase #3	$109.41	13.262%	$123.92	$123.92	$123.90	$123.90
Purchase #4	$242.46	7.550%	$260.7657	$260.77	$260.75	$260.80
Purchase #5	$210.95	10.544%	$233.1926	$233.19	$233.20	$233.20
Purchase #6	$204.78	8.110%	$221.3877	$221.39	$221.40	$221.40
Purchase #7	$139.41	12.469%	$156.793	$156.79	$156.80	$156.80
7 purchase totals =	$1,153.89		$1,255.4817	$1,255.48	$1,255.45	$1,255.50