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 $77.48   13.538%   $87.9692   $87.97   $87.95   $88.00  
  Purchase #2 $104.41   13.689%   $118.7027   $118.70   $118.70   $118.70  
  Purchase #3 $44.99   8.691%   $48.9001   $48.90   $48.90   $48.90  
  Purchase #4 $68.74   4.822%   $72.0546   $72.05   $72.05   $72.10  
  Purchase #5 $151.93   3.286%   $156.9224   $156.92   $156.90   $156.90  
  Purchase #6 $180.92   5.112%   $190.1686   $190.17   $190.15   $190.20  
  Purchase #7 $83.36   5.388%   $87.8514   $87.85   $87.85   $87.90  
  7 purchase totals = $711.83       $762.5690   $762.56   $762.50   $762.70