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 $60.84   8.380%   $65.9384   $65.94   $65.95   $65.90  
  Purchase #2 $196.31   5.808%   $207.7117   $207.71   $207.70   $207.70  
  Purchase #3 $222.31   6.455%   $236.6601   $236.66   $236.65   $236.70  
  Purchase #4 $245.96   13.464%   $279.0761   $279.08   $279.10   $279.10  
  Purchase #5 $167.56   4.598%   $175.2644   $175.26   $175.25   $175.30  
  Purchase #6 $54.72   12.675%   $61.6558   $61.66   $61.65   $61.70  
  Purchase #7 $25.56   12.237%   $28.6878   $28.69   $28.70   $28.70  
  7 purchase totals = $973.26       $1,054.9943   $1,055.00   $1,055.00   $1,055.10