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	$85.75	5.604%	$90.5554	$90.56	$90.55	$90.60
Purchase #2	$208.86	6.496%	$222.4275	$222.43	$222.45	$222.40
Purchase #3	$33.55	12.175%	$37.6347	$37.63	$37.65	$37.60
Purchase #4	$230.48	11.638%	$257.3033	$257.30	$257.30	$257.30
Purchase #5	$49.70	6.396%	$52.8788	$52.88	$52.90	$52.90
Purchase #6	$246.89	13.316%	$279.7659	$279.77	$279.75	$279.80
Purchase #7	$77.60	7.435%	$83.3696	$83.37	$83.35	$83.40
7 purchase totals =	$932.83		$1,023.9352	$1,023.94	$1,023.95	$1,024.00