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 $86.80   6.616%   $92.5427   $92.54   $92.55   $92.50  
  Purchase #2 $208.27   10.699%   $230.5528   $230.55   $230.55   $230.60  
  Purchase #3 $113.97   11.338%   $126.8919   $126.89   $126.90   $126.90  
  Purchase #4 $230.96   8.267%   $250.0535   $250.05   $250.05   $250.10  
  Purchase #5 $117.42   10.214%   $129.4133   $129.41   $129.40   $129.40  
  Purchase #6 $56.95   13.294%   $64.5209   $64.52   $64.50   $64.50  
  Purchase #7 $133.89   5.336%   $141.0344   $141.03   $141.05   $141.00  
  7 purchase totals = $948.26       $1,035.0095   $1,034.99   $1,035.00   $1,035.00