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 $60.47   8.227%   $65.4449   $65.44   $65.45   $65.40  
  Purchase #2 $244.44   8.454%   $265.105   $265.11   $265.10   $265.10  
  Purchase #3 $55.44   9.289%   $60.5898   $60.59   $60.60   $60.60  
  Purchase #4 $55.93   12.134%   $62.7165   $62.72   $62.70   $62.70  
  Purchase #5 $187.52   7.609%   $201.7884   $201.79   $201.80   $201.80  
  Purchase #6 $164.93   10.334%   $181.9739   $181.97   $181.95   $182.00  
  Purchase #7 $231.39   11.529%   $258.067   $258.07   $258.05   $258.10  
  7 purchase totals = $1,000.12       $1,095.6855   $1,095.69   $1,095.65   $1,095.70