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 $58.34   6.274%   $62.0003   $62.00   $62.00   $62.00  
  Purchase #2 $113.53   7.807%   $122.3933   $122.39   $122.40   $122.40  
  Purchase #3 $137.84   8.602%   $149.697   $149.70   $149.70   $149.70  
  Purchase #4 $112.78   8.535%   $122.4058   $122.41   $122.40   $122.40  
  Purchase #5 $11.65   6.678%   $12.428   $12.43   $12.45   $12.40  
  Purchase #6 $64.99   10.726%   $71.9608   $71.96   $71.95   $72.00  
  Purchase #7 $205.76   12.384%   $231.2413   $231.24   $231.25   $231.20  
  7 purchase totals = $704.89       $772.1265   $772.13   $772.15   $772.10