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 $59.75   5.374%   $62.961   $62.96   $62.95   $63.00  
  Purchase #2 $248.72   7.241%   $266.7298   $266.73   $266.75   $266.70  
  Purchase #3 $68.46   8.371%   $74.1908   $74.19   $74.20   $74.20  
  Purchase #4 $8.45   5.759%   $8.9366   $8.94   $8.95   $8.90  
  Purchase #5 $55.83   13.311%   $63.2615   $63.26   $63.25   $63.30  
  Purchase #6 $208.58   9.761%   $228.9395   $228.94   $228.95   $228.90  
  Purchase #7 $155.59   12.774%   $175.4651   $175.47   $175.45   $175.50  
  7 purchase totals = $805.38       $880.4843   $880.49   $880.50   $880.50