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	$33.62	3.451%	$34.7802	$34.78	$34.80	$34.80
Purchase #2	$244.50	5.266%	$257.3754	$257.38	$257.40	$257.40
Purchase #3	$248.90	13.604%	$282.7604	$282.76	$282.75	$282.80
Purchase #4	$185.57	8.235%	$200.8517	$200.85	$200.85	$200.90
Purchase #5	$88.47	11.594%	$98.7272	$98.73	$98.75	$98.70
Purchase #6	$126.49	4.186%	$131.7849	$131.78	$131.80	$131.80
Purchase #7	$61.60	4.777%	$64.5426	$64.54	$64.55	$64.50
7 purchase totals =	$989.15		$1,070.8224	$1,070.82	$1,070.90	$1,070.90