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	$39.86	7.872%	$42.9978	$43.00	$43.00	$43.00
Purchase #2	$82.61	11.702%	$92.277	$92.28	$92.30	$92.30
Purchase #3	$97.83	4.774%	$102.5004	$102.50	$102.50	$102.50
Purchase #4	$241.69	8.737%	$262.8065	$262.81	$262.80	$262.80
Purchase #5	$78.94	5.576%	$83.3417	$83.34	$83.35	$83.30
Purchase #6	$136.56	11.405%	$152.1347	$152.13	$152.15	$152.10
Purchase #7	$124.89	6.179%	$132.607	$132.61	$132.60	$132.60
7 purchase totals =	$802.38		$868.6651	$868.67	$868.70	$868.60