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	$120.69	8.763%	$131.2661	$131.27	$131.25	$131.30
Purchase #2	$9.39	11.319%	$10.4529	$10.45	$10.45	$10.50
Purchase #3	$222.85	5.232%	$234.5095	$234.51	$234.50	$234.50
Purchase #4	$41.31	13.576%	$46.9182	$46.92	$46.90	$46.90
Purchase #5	$54.93	8.421%	$59.5557	$59.56	$59.55	$59.60
Purchase #6	$182.60	13.695%	$207.6071	$207.61	$207.60	$207.60
Purchase #7	$63.94	9.863%	$70.2464	$70.25	$70.25	$70.20
7 purchase totals =	$695.71		$760.5559	$760.57	$760.50	$760.60