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 $68.28   9.689%   $74.8956   $74.90   $74.90   $74.90  
  Purchase #2 $43.58   3.873%   $45.2679   $45.27   $45.25   $45.30  
  Purchase #3 $16.64   4.604%   $17.4061   $17.41   $17.40   $17.40  
  Purchase #4 $62.57   5.268%   $65.8662   $65.87   $65.85   $65.90  
  Purchase #5 $64.65   11.284%   $71.9451   $71.95   $71.95   $71.90  
  Purchase #6 $202.46   6.844%   $216.3164   $216.32   $216.30   $216.30  
  Purchase #7 $195.33   6.391%   $207.8135   $207.81   $207.80   $207.80  
  7 purchase totals = $653.51       $699.5108   $699.53   $699.45   $699.50