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 $54.97   10.185%   $60.5687   $60.57   $60.55   $60.60  
  Purchase #2 $205.42   5.300%   $216.3073   $216.31   $216.30   $216.30  
  Purchase #3 $74.83   10.214%   $82.4731   $82.47   $82.45   $82.50  
  Purchase #4 $155.36   4.109%   $161.7437   $161.74   $161.75   $161.70  
  Purchase #5 $129.87   9.107%   $141.6973   $141.70   $141.70   $141.70  
  Purchase #6 $196.29   9.628%   $215.1888   $215.19   $215.20   $215.20  
  Purchase #7 $66.89   6.146%   $71.0011   $71.00   $71.00   $71.00  
  7 purchase totals = $883.63       $948.9800   $948.98   $948.95   $949.00