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 $62.50   10.406%   $69.0038   $69.00   $69.00   $69.00  
  Purchase #2 $146.63   8.213%   $158.6727   $158.67   $158.65   $158.70  
  Purchase #3 $211.58   13.790%   $240.7569   $240.76   $240.75   $240.80  
  Purchase #4 $186.83   5.287%   $196.7077   $196.71   $196.70   $196.70  
  Purchase #5 $235.59   10.711%   $260.824   $260.82   $260.80   $260.80  
  Purchase #6 $106.59   13.282%   $120.7473   $120.75   $120.75   $120.70  
  Purchase #7 $210.78   4.651%   $220.5834   $220.58   $220.60   $220.60  
  7 purchase totals = $1,160.50       $1,267.2958   $1,267.29   $1,267.25   $1,267.30