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	$188.26	4.158%	$196.0879	$196.09	$196.10	$196.10
Purchase #2	$158.76	3.628%	$164.5198	$164.52	$164.50	$164.50
Purchase #3	$125.59	10.184%	$138.3801	$138.38	$138.40	$138.40
Purchase #4	$26.27	3.762%	$27.2583	$27.26	$27.25	$27.30
Purchase #5	$92.75	10.521%	$102.5082	$102.51	$102.50	$102.50
Purchase #6	$250.94	5.675%	$265.1808	$265.18	$265.20	$265.20
Purchase #7	$41.83	8.167%	$45.2463	$45.25	$45.25	$45.20
7 purchase totals =	$884.40		$939.1814	$939.19	$939.20	$939.20