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 $68.31   9.168%   $74.5727   $74.57   $74.55   $74.60  
  Purchase #2 $102.62   8.396%   $111.236   $111.24   $111.25   $111.20  
  Purchase #3 $61.58   13.482%   $69.8822   $69.88   $69.90   $69.90  
  Purchase #4 $151.54   3.862%   $157.3925   $157.39   $157.40   $157.40  
  Purchase #5 $238.88   7.723%   $257.3287   $257.33   $257.35   $257.30  
  Purchase #6 $231.59   4.788%   $242.6785   $242.68   $242.70   $242.70  
  Purchase #7 $90.25   11.753%   $100.8571   $100.86   $100.85   $100.90  
  7 purchase totals = $944.77       $1,013.9477   $1,013.95   $1,014.00   $1,014.00