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	$83.59	12.507%	$94.0446	$94.04	$94.05	$94.00
Purchase #2	$199.25	5.211%	$209.6329	$209.63	$209.65	$209.60
Purchase #3	$20.89	7.342%	$22.4237	$22.42	$22.40	$22.40
Purchase #4	$120.58	10.212%	$132.8936	$132.89	$132.90	$132.90
Purchase #5	$52.97	11.812%	$59.2268	$59.23	$59.25	$59.20
Purchase #6	$60.56	6.457%	$64.4704	$64.47	$64.45	$64.50
Purchase #7	$59.80	13.179%	$67.681	$67.68	$67.70	$67.70
7 purchase totals =	$597.64		$650.3730	$650.36	$650.40	$650.30