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	$216.98	10.363%	$239.4656	$239.47	$239.45	$239.50
Purchase #2	$242.39	9.371%	$265.1044	$265.10	$265.10	$265.10
Purchase #3	$38.65	8.384%	$41.8904	$41.89	$41.90	$41.90
Purchase #4	$7.28	6.533%	$7.7556	$7.76	$7.75	$7.80
Purchase #5	$198.50	8.738%	$215.8449	$215.84	$215.85	$215.80
Purchase #6	$219.88	11.229%	$244.5703	$244.57	$244.55	$244.60
Purchase #7	$54.40	13.510%	$61.7494	$61.75	$61.75	$61.70
7 purchase totals =	$978.08		$1,076.3806	$1,076.38	$1,076.35	$1,076.40