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	$234.95	5.162%	$247.0781	$247.08	$247.10	$247.10
Purchase #2	$82.92	4.235%	$86.4317	$86.43	$86.45	$86.40
Purchase #3	$80.84	8.583%	$87.7785	$87.78	$87.80	$87.80
Purchase #4	$16.73	9.705%	$18.3536	$18.35	$18.35	$18.40
Purchase #5	$124.32	5.684%	$131.3863	$131.39	$131.40	$131.40
Purchase #6	$85.52	5.858%	$90.5298	$90.53	$90.55	$90.50
Purchase #7	$64.88	6.712%	$69.2347	$69.23	$69.25	$69.20
7 purchase totals =	$690.16		$730.7927	$730.79	$730.90	$730.80