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	$40.42	9.333%	$44.1924	$44.19	$44.20	$44.20
Purchase #2	$82.68	3.324%	$85.4283	$85.43	$85.45	$85.40
Purchase #3	$243.69	3.128%	$251.3126	$251.31	$251.30	$251.30
Purchase #4	$83.51	4.143%	$86.9698	$86.97	$86.95	$87.00
Purchase #5	$43.83	4.641%	$45.8642	$45.86	$45.85	$45.90
Purchase #6	$105.46	3.564%	$109.2186	$109.22	$109.20	$109.20
Purchase #7	$55.95	5.867%	$59.2326	$59.23	$59.25	$59.20
7 purchase totals =	$655.54		$682.2185	$682.21	$682.20	$682.20