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 $196.68   5.317%   $207.1375   $207.14   $207.15   $207.10  
  Purchase #2 $167.66   12.170%   $188.0642   $188.06   $188.05   $188.10  
  Purchase #3 $78.88   10.631%   $87.2657   $87.27   $87.25   $87.30  
  Purchase #4 $92.98   10.609%   $102.8442   $102.84   $102.85   $102.80  
  Purchase #5 $151.74   12.642%   $170.923   $170.92   $170.90   $170.90  
  Purchase #6 $245.70   11.601%   $274.2037   $274.20   $274.20   $274.20  
  Purchase #7 $189.79   7.798%   $204.5898   $204.59   $204.60   $204.60  
  7 purchase totals = $1,123.43       $1,235.0281   $1,235.02   $1,235.00   $1,235.00