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 $179.61   8.747%   $195.3205   $195.32   $195.30   $195.30  
  Purchase #2 $23.95   7.498%   $25.7458   $25.75   $25.75   $25.70  
  Purchase #3 $36.84   6.143%   $39.1031   $39.10   $39.10   $39.10  
  Purchase #4 $44.35   13.720%   $50.4348   $50.43   $50.45   $50.40  
  Purchase #5 $26.32   5.107%   $27.6642   $27.66   $27.65   $27.70  
  Purchase #6 $62.55   13.734%   $71.1406   $71.14   $71.15   $71.10  
  Purchase #7 $55.57   5.135%   $58.4235   $58.42   $58.40   $58.40  
  7 purchase totals = $429.19       $467.8325   $467.82   $467.80   $467.70