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	$55.50	7.802%	$59.8301	$59.83	$59.85	$59.80
Purchase #2	$40.63	3.275%	$41.9606	$41.96	$41.95	$42.00
Purchase #3	$32.96	10.413%	$36.3921	$36.39	$36.40	$36.40
Purchase #4	$63.37	5.795%	$67.0423	$67.04	$67.05	$67.00
Purchase #5	$182.61	3.685%	$189.3392	$189.34	$189.35	$189.30
Purchase #6	$76.47	9.160%	$83.4747	$83.47	$83.45	$83.50
Purchase #7	$225.37	12.685%	$253.9582	$253.96	$253.95	$254.00
7 purchase totals =	$676.91		$731.9972	$731.99	$732.00	$732.00