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	$37.58	10.162%	$41.3989	$41.40	$41.40	$41.40
Purchase #2	$137.26	5.702%	$145.0866	$145.09	$145.10	$145.10
Purchase #3	$234.34	12.844%	$264.4386	$264.44	$264.45	$264.40
Purchase #4	$227.39	3.279%	$234.8461	$234.85	$234.85	$234.80
Purchase #5	$222.43	12.604%	$250.4651	$250.47	$250.45	$250.50
Purchase #6	$159.27	3.409%	$164.6995	$164.70	$164.70	$164.70
Purchase #7	$125.44	13.473%	$142.3405	$142.34	$142.35	$142.30
7 purchase totals =	$1,143.71		$1,243.2753	$1,243.29	$1,243.30	$1,243.20