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 $208.97   6.586%   $222.7328   $222.73   $222.75   $222.70  
  Purchase #2 $211.81   7.527%   $227.7529   $227.75   $227.75   $227.80  
  Purchase #3 $5.93   6.764%   $6.3311   $6.33   $6.35   $6.30  
  Purchase #4 $43.46   9.572%   $47.62   $47.62   $47.60   $47.60  
  Purchase #5 $93.99   3.496%   $97.2759   $97.28   $97.30   $97.30  
  Purchase #6 $53.73   4.147%   $55.9582   $55.96   $55.95   $56.00  
  Purchase #7 $55.39   3.478%   $57.3165   $57.32   $57.30   $57.30  
  7 purchase totals = $673.28       $714.9874   $714.99   $715.00   $715.00