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 $193.43   4.506%   $202.146   $202.15   $202.15   $202.10  
  Purchase #2 $111.41   9.745%   $122.2669   $122.27   $122.25   $122.30  
  Purchase #3 $68.73   8.656%   $74.6793   $74.68   $74.70   $74.70  
  Purchase #4 $182.72   8.133%   $197.5806   $197.58   $197.60   $197.60  
  Purchase #5 $163.59   12.604%   $184.2089   $184.21   $184.20   $184.20  
  Purchase #6 $68.42   11.810%   $76.5004   $76.50   $76.50   $76.50  
  Purchase #7 $220.97   10.229%   $243.573   $243.57   $243.55   $243.60  
  7 purchase totals = $1,009.27       $1,100.9551   $1,100.96   $1,100.95   $1,101.00