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	$67.49	12.772%	$76.1098	$76.11	$76.10	$76.10
Purchase #2	$92.83	13.685%	$105.5338	$105.53	$105.55	$105.50
Purchase #3	$141.63	11.248%	$157.5605	$157.56	$157.55	$157.60
Purchase #4	$75.84	8.715%	$82.4495	$82.45	$82.45	$82.40
Purchase #5	$206.65	8.436%	$224.083	$224.08	$224.10	$224.10
Purchase #6	$238.45	7.496%	$256.3242	$256.32	$256.30	$256.30
Purchase #7	$134.75	5.433%	$142.071	$142.07	$142.05	$142.10
7 purchase totals =	$957.64		$1,044.1318	$1,044.12	$1,044.10	$1,044.10