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	$104.29	13.708%	$118.5861	$118.59	$118.60	$118.60
Purchase #2	$96.25	12.218%	$108.0098	$108.01	$108.00	$108.00
Purchase #3	$206.78	8.139%	$223.6098	$223.61	$223.60	$223.60
Purchase #4	$88.41	4.601%	$92.4777	$92.48	$92.50	$92.50
Purchase #5	$53.48	7.353%	$57.4124	$57.41	$57.40	$57.40
Purchase #6	$98.76	5.303%	$103.9972	$104.00	$104.00	$104.00
Purchase #7	$179.61	10.310%	$198.1278	$198.13	$198.15	$198.10
7 purchase totals =	$827.58		$902.2208	$902.23	$902.25	$902.20