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	$88.91	5.724%	$93.9992	$94.00	$94.00	$94.00
Purchase #2	$156.44	10.412%	$172.7285	$172.73	$172.75	$172.70
Purchase #3	$66.70	11.362%	$74.2785	$74.28	$74.30	$74.30
Purchase #4	$242.59	13.136%	$274.4566	$274.46	$274.45	$274.50
Purchase #5	$128.46	10.453%	$141.8879	$141.89	$141.90	$141.90
Purchase #6	$144.54	5.704%	$152.7846	$152.78	$152.80	$152.80
Purchase #7	$135.64	5.410%	$142.9781	$142.98	$143.00	$143.00
7 purchase totals =	$963.28		$1,053.1134	$1,053.12	$1,053.20	$1,053.20