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	$85.96	10.384%	$94.8861	$94.89	$94.90	$94.90
Purchase #2	$68.41	13.145%	$77.4025	$77.40	$77.40	$77.40
Purchase #3	$186.71	9.385%	$204.2327	$204.23	$204.25	$204.20
Purchase #4	$199.72	10.551%	$220.7925	$220.79	$220.80	$220.80
Purchase #5	$38.36	10.789%	$42.4987	$42.50	$42.50	$42.50
Purchase #6	$45.78	6.770%	$48.8793	$48.88	$48.90	$48.90
Purchase #7	$63.43	3.299%	$65.5226	$65.52	$65.50	$65.50
7 purchase totals =	$688.37		$754.2144	$754.21	$754.25	$754.20