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 $56.41   11.453%   $62.8706   $62.87   $62.85   $62.90  
  Purchase #2 $210.82   8.549%   $228.843   $228.84   $228.85   $228.80  
  Purchase #3 $98.56   5.134%   $103.6201   $103.62   $103.60   $103.60  
  Purchase #4 $181.49   6.854%   $193.9293   $193.93   $193.95   $193.90  
  Purchase #5 $17.61   12.109%   $19.7424   $19.74   $19.75   $19.70  
  Purchase #6 $59.74   4.527%   $62.4444   $62.44   $62.45   $62.40  
  Purchase #7 $67.27   5.552%   $71.0048   $71.00   $71.00   $71.00  
  7 purchase totals = $691.90       $742.4546   $742.44   $742.45   $742.30