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	$49.42	5.395%	$52.0862	$52.09	$52.10	$52.10
Purchase #2	$186.80	6.203%	$198.3872	$198.39	$198.40	$198.40
Purchase #3	$116.51	5.811%	$123.2804	$123.28	$123.30	$123.30
Purchase #4	$130.96	5.595%	$138.2872	$138.29	$138.30	$138.30
Purchase #5	$72.51	3.582%	$75.1073	$75.11	$75.10	$75.10
Purchase #6	$78.35	5.527%	$82.6804	$82.68	$82.70	$82.70
Purchase #7	$64.87	11.759%	$72.4981	$72.50	$72.50	$72.50
7 purchase totals =	$699.42		$742.3268	$742.34	$742.40	$742.40