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	$42.61	10.632%	$47.1403	$47.14	$47.15	$47.10
Purchase #2	$90.70	4.755%	$95.0128	$95.01	$95.00	$95.00
Purchase #3	$32.78	12.803%	$36.9768	$36.98	$37.00	$37.00
Purchase #4	$122.60	7.645%	$131.9728	$131.97	$131.95	$132.00
Purchase #5	$167.66	12.766%	$189.0635	$189.06	$189.05	$189.10
Purchase #6	$227.93	5.249%	$239.894	$239.89	$239.90	$239.90
Purchase #7	$100.71	10.221%	$111.0036	$111.00	$111.00	$111.00
7 purchase totals =	$784.99		$851.0638	$851.05	$851.05	$851.10