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 $213.56   11.260%   $237.6069   $237.61   $237.60   $237.60  
  Purchase #2 $100.26   11.664%   $111.9543   $111.95   $111.95   $112.00  
  Purchase #3 $34.34   5.410%   $36.1978   $36.20   $36.20   $36.20  
  Purchase #4 $240.86   7.536%   $259.0112   $259.01   $259.00   $259.00  
  Purchase #5 $188.90   4.375%   $197.1644   $197.16   $197.15   $197.20  
  Purchase #6 $245.26   7.870%   $264.562   $264.56   $264.55   $264.60  
  Purchase #7 $104.61   6.122%   $111.0142   $111.01   $111.00   $111.00  
  7 purchase totals = $1,127.79       $1,217.5108   $1,217.50   $1,217.45   $1,217.60