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	$200.81	8.349%	$217.5756	$217.58	$217.60	$217.60
Purchase #2	$138.34	10.479%	$152.8366	$152.84	$152.85	$152.80
Purchase #3	$56.83	8.139%	$61.4554	$61.46	$61.45	$61.50
Purchase #4	$41.36	12.756%	$46.6359	$46.64	$46.65	$46.60
Purchase #5	$19.64	5.472%	$20.7147	$20.71	$20.70	$20.70
Purchase #6	$78.55	6.227%	$83.4413	$83.44	$83.45	$83.40
Purchase #7	$161.55	8.669%	$175.5548	$175.55	$175.55	$175.60
7 purchase totals =	$697.08		$758.2143	$758.22	$758.25	$758.20