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 $84.26   12.765%   $95.0158   $95.02   $95.00   $95.00  
  Purchase #2 $60.92   9.610%   $66.7744   $66.77   $66.75   $66.80  
  Purchase #3 $234.67   4.652%   $245.5868   $245.59   $245.60   $245.60  
  Purchase #4 $179.34   6.806%   $191.5459   $191.55   $191.55   $191.50  
  Purchase #5 $19.57   7.468%   $21.0315   $21.03   $21.05   $21.00  
  Purchase #6 $222.86   6.669%   $237.7225   $237.72   $237.70   $237.70  
  Purchase #7 $121.96   4.467%   $127.408   $127.41   $127.40   $127.40  
  7 purchase totals = $923.58       $985.0849   $985.09   $985.05   $985.00