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	$218.35	5.271%	$229.8592	$229.86	$229.85	$229.90
Purchase #2	$152.90	6.247%	$162.4517	$162.45	$162.45	$162.50
Purchase #3	$105.63	10.334%	$116.5458	$116.55	$116.55	$116.50
Purchase #4	$20.70	8.366%	$22.4318	$22.43	$22.45	$22.40
Purchase #5	$12.78	9.294%	$13.9678	$13.97	$13.95	$14.00
Purchase #6	$75.85	9.155%	$82.7941	$82.79	$82.80	$82.80
Purchase #7	$80.50	11.336%	$89.6255	$89.63	$89.65	$89.60
7 purchase totals =	$666.71		$717.6759	$717.68	$717.70	$717.70