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 $69.28   7.599%   $74.5446   $74.54   $74.55   $74.50  
  Purchase #2 $169.77   7.646%   $182.7506   $182.75   $182.75   $182.80  
  Purchase #3 $64.28   11.456%   $71.6439   $71.64   $71.65   $71.60  
  Purchase #4 $153.97   7.798%   $165.9766   $165.98   $166.00   $166.00  
  Purchase #5 $143.63   13.673%   $163.2685   $163.27   $163.25   $163.30  
  Purchase #6 $71.74   5.514%   $75.6957   $75.70   $75.70   $75.70  
  Purchase #7 $21.80   5.764%   $23.0566   $23.06   $23.05   $23.10  
  7 purchase totals = $694.47       $756.9365   $756.94   $756.95   $757.00