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 $191.46   8.597%   $207.9198   $207.92   $207.90   $207.90  
  Purchase #2 $241.59   10.773%   $267.6165   $267.62   $267.60   $267.60  
  Purchase #3 $218.70   12.658%   $246.383   $246.38   $246.40   $246.40  
  Purchase #4 $77.66   11.538%   $86.6204   $86.62   $86.60   $86.60  
  Purchase #5 $95.41   7.795%   $102.8472   $102.85   $102.85   $102.80  
  Purchase #6 $61.42   6.617%   $65.4842   $65.48   $65.50   $65.50  
  Purchase #7 $220.99   5.582%   $233.3257   $233.33   $233.35   $233.30  
  7 purchase totals = $1,107.23       $1,210.1968   $1,210.20   $1,210.20   $1,210.10