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	$167.36	3.330%	$172.9331	$172.93	$172.95	$172.90
Purchase #2	$83.93	4.471%	$87.6825	$87.68	$87.70	$87.70
Purchase #3	$125.53	12.474%	$141.1886	$141.19	$141.20	$141.20
Purchase #4	$219.66	5.365%	$231.4448	$231.44	$231.45	$231.40
Purchase #5	$38.73	6.687%	$41.3199	$41.32	$41.30	$41.30
Purchase #6	$250.78	8.680%	$272.5477	$272.55	$272.55	$272.50
Purchase #7	$145.73	13.142%	$164.8818	$164.88	$164.90	$164.90
7 purchase totals =	$1,031.72		$1,111.9984	$1,111.99	$1,112.05	$1,111.90