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 $59.36   6.622%   $63.2908   $63.29   $63.30   $63.30  
  Purchase #2 $201.91   5.277%   $212.5648   $212.56   $212.55   $212.60  
  Purchase #3 $175.42   4.249%   $182.8736   $182.87   $182.85   $182.90  
  Purchase #4 $162.48   8.168%   $175.7514   $175.75   $175.75   $175.80  
  Purchase #5 $164.49   12.836%   $185.6039   $185.60   $185.60   $185.60  
  Purchase #6 $35.83   7.840%   $38.6391   $38.64   $38.65   $38.60  
  Purchase #7 $225.26   9.288%   $246.1821   $246.18   $246.20   $246.20  
  7 purchase totals = $1,024.75       $1,104.9057   $1,104.89   $1,104.90   $1,105.00