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 $116.75   7.814%   $125.8728   $125.87   $125.85   $125.90  
  Purchase #2 $82.69   6.632%   $88.174   $88.17   $88.15   $88.20  
  Purchase #3 $56.96   11.708%   $63.6289   $63.63   $63.65   $63.60  
  Purchase #4 $212.58   10.199%   $234.261   $234.26   $234.25   $234.30  
  Purchase #5 $90.41   6.136%   $95.9576   $95.96   $95.95   $96.00  
  Purchase #6 $232.55   8.527%   $252.3795   $252.38   $252.40   $252.40  
  Purchase #7 $32.66   7.641%   $35.1556   $35.16   $35.15   $35.20  
  7 purchase totals = $824.60       $895.4294   $895.43   $895.40   $895.60