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 $56.87   9.122%   $62.0577   $62.06   $62.05   $62.10  
  Purchase #2 $156.92   6.720%   $167.465   $167.47   $167.45   $167.50  
  Purchase #3 $66.75   3.408%   $69.0248   $69.02   $69.00   $69.00  
  Purchase #4 $126.32   6.633%   $134.6988   $134.70   $134.70   $134.70  
  Purchase #5 $95.34   8.825%   $103.7538   $103.75   $103.75   $103.80  
  Purchase #6 $170.60   6.212%   $181.1977   $181.20   $181.20   $181.20  
  Purchase #7 $246.82   11.277%   $274.6539   $274.65   $274.65   $274.70  
  7 purchase totals = $919.62       $992.8517   $992.85   $992.80   $993.00