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	$150.61	13.249%	$170.5643	$170.56	$170.55	$170.60
Purchase #2	$73.51	6.284%	$78.1294	$78.13	$78.15	$78.10
Purchase #3	$141.59	10.181%	$156.0053	$156.01	$156.00	$156.00
Purchase #4	$233.67	11.375%	$260.25	$260.25	$260.25	$260.30
Purchase #5	$105.36	5.727%	$111.394	$111.39	$111.40	$111.40
Purchase #6	$67.98	12.176%	$76.2572	$76.26	$76.25	$76.30
Purchase #7	$139.93	12.617%	$157.585	$157.59	$157.60	$157.60
7 purchase totals =	$912.65		$1,010.1852	$1,010.19	$1,010.20	$1,010.30