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	$202.83	9.747%	$222.5998	$222.60	$222.60	$222.60
Purchase #2	$26.57	9.864%	$29.1909	$29.19	$29.20	$29.20
Purchase #3	$39.70	8.196%	$42.9538	$42.95	$42.95	$43.00
Purchase #4	$107.77	10.720%	$119.3229	$119.32	$119.30	$119.30
Purchase #5	$136.90	4.797%	$143.4671	$143.47	$143.45	$143.50
Purchase #6	$42.91	10.277%	$47.3199	$47.32	$47.30	$47.30
Purchase #7	$127.32	3.271%	$131.4846	$131.48	$131.50	$131.50
7 purchase totals =	$684.00		$736.3390	$736.33	$736.30	$736.40