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 $60.46   10.744%   $66.9558   $66.96   $66.95   $67.00  
  Purchase #2 $234.89   5.871%   $248.6804   $248.68   $248.70   $248.70  
  Purchase #3 $119.63   3.175%   $123.4283   $123.43   $123.45   $123.40  
  Purchase #4 $79.69   10.830%   $88.3204   $88.32   $88.30   $88.30  
  Purchase #5 $99.34   8.397%   $107.6816   $107.68   $107.70   $107.70  
  Purchase #6 $104.38   12.850%   $117.7928   $117.79   $117.80   $117.80  
  Purchase #7 $243.72   4.437%   $254.5339   $254.53   $254.55   $254.50  
  7 purchase totals = $942.11       $1,007.3932   $1,007.39   $1,007.45   $1,007.40