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	$172.30	5.217%	$181.2889	$181.29	$181.30	$181.30
Purchase #2	$51.55	3.713%	$53.4641	$53.46	$53.45	$53.50
Purchase #3	$23.58	5.826%	$24.9538	$24.95	$24.95	$25.00
Purchase #4	$43.92	3.672%	$45.5327	$45.53	$45.55	$45.50
Purchase #5	$38.34	9.241%	$41.883	$41.88	$41.90	$41.90
Purchase #6	$148.78	3.514%	$154.0081	$154.01	$154.00	$154.00
Purchase #7	$223.78	3.327%	$231.2252	$231.23	$231.25	$231.20
7 purchase totals =	$702.25		$732.3558	$732.35	$732.40	$732.40