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 $62.89   9.721%   $69.0035   $69.00   $69.00   $69.00  
  Purchase #2 $201.84   3.516%   $208.9367   $208.94   $208.95   $208.90  
  Purchase #3 $65.94   11.417%   $73.4684   $73.47   $73.45   $73.50  
  Purchase #4 $140.37   4.481%   $146.66   $146.66   $146.65   $146.70  
  Purchase #5 $162.60   11.326%   $181.0161   $181.02   $181.00   $181.00  
  Purchase #6 $109.83   3.388%   $113.551   $113.55   $113.55   $113.60  
  Purchase #7 $224.34   8.576%   $243.5794   $243.58   $243.60   $243.60  
  7 purchase totals = $967.81       $1,036.2151   $1,036.22   $1,036.20   $1,036.30