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	$244.69	4.814%	$256.4694	$256.47	$256.45	$256.50
Purchase #2	$16.80	9.723%	$18.4335	$18.43	$18.45	$18.40
Purchase #3	$109.77	8.402%	$118.9929	$118.99	$119.00	$119.00
Purchase #4	$126.30	6.300%	$134.2569	$134.26	$134.25	$134.30
Purchase #5	$168.31	10.370%	$185.7637	$185.76	$185.75	$185.80
Purchase #6	$162.61	10.644%	$179.9182	$179.92	$179.90	$179.90
Purchase #7	$175.88	9.218%	$192.0926	$192.09	$192.10	$192.10
7 purchase totals =	$1,004.36		$1,085.9272	$1,085.92	$1,085.90	$1,086.00