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 $232.99   5.174%   $245.0449   $245.04   $245.05   $245.00  
  Purchase #2 $147.81   4.540%   $154.5206   $154.52   $154.50   $154.50  
  Purchase #3 $132.30   12.394%   $148.6973   $148.70   $148.70   $148.70  
  Purchase #4 $171.89   13.629%   $195.3169   $195.32   $195.30   $195.30  
  Purchase #5 $250.54   5.535%   $264.4074   $264.41   $264.40   $264.40  
  Purchase #6 $62.54   9.605%   $68.547   $68.55   $68.55   $68.50  
  Purchase #7 $16.61   5.435%   $17.5128   $17.51   $17.50   $17.50  
  7 purchase totals = $1,014.68       $1,094.0469   $1,094.05   $1,094.00   $1,093.90