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 $46.27   5.206%   $48.6788   $48.68   $48.70   $48.70  
  Purchase #2 $217.26   5.756%   $229.7655   $229.77   $229.75   $229.80  
  Purchase #3 $139.65   7.118%   $149.5903   $149.59   $149.60   $149.60  
  Purchase #4 $67.39   12.812%   $76.024   $76.02   $76.00   $76.00  
  Purchase #5 $180.35   7.241%   $193.4091   $193.41   $193.40   $193.40  
  Purchase #6 $156.80   12.763%   $176.8124   $176.81   $176.80   $176.80  
  Purchase #7 $187.86   7.282%   $201.54   $201.54   $201.55   $201.50  
  7 purchase totals = $995.58       $1,075.8201   $1,075.82   $1,075.80   $1,075.80