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 $58.83   5.401%   $62.0074   $62.01   $62.00   $62.00  
  Purchase #2 $129.69   8.404%   $140.5891   $140.59   $140.60   $140.60  
  Purchase #3 $112.39   11.274%   $125.0608   $125.06   $125.05   $125.10  
  Purchase #4 $166.92   4.125%   $173.8055   $173.81   $173.80   $173.80  
  Purchase #5 $109.98   3.363%   $113.6786   $113.68   $113.70   $113.70  
  Purchase #6 $237.33   3.393%   $245.3826   $245.38   $245.40   $245.40  
  Purchase #7 $213.86   4.760%   $224.0397   $224.04   $224.05   $224.00  
  7 purchase totals = $1,029.00       $1,084.5637   $1,084.57   $1,084.60   $1,084.60