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 $116.71   4.275%   $121.6994   $121.70   $121.70   $121.70  
  Purchase #2 $125.54   10.820%   $139.1234   $139.12   $139.10   $139.10  
  Purchase #3 $175.27   10.396%   $193.4911   $193.49   $193.50   $193.50  
  Purchase #4 $67.50   6.407%   $71.8247   $71.82   $71.80   $71.80  
  Purchase #5 $144.76   7.460%   $155.5591   $155.56   $155.55   $155.60  
  Purchase #6 $181.69   8.727%   $197.5461   $197.55   $197.55   $197.50  
  Purchase #7 $68.36   3.546%   $70.784   $70.78   $70.80   $70.80  
  7 purchase totals = $879.83       $950.0278   $950.02   $950.00   $950.00