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 $152.67   5.561%   $161.16   $161.16   $161.15   $161.20  
  Purchase #2 $239.51   5.257%   $252.101   $252.10   $252.10   $252.10  
  Purchase #3 $161.32   13.406%   $182.9466   $182.95   $182.95   $182.90  
  Purchase #4 $93.84   4.507%   $98.0694   $98.07   $98.05   $98.10  
  Purchase #5 $87.78   6.821%   $93.7675   $93.77   $93.75   $93.80  
  Purchase #6 $144.94   12.644%   $163.2662   $163.27   $163.25   $163.30  
  Purchase #7 $241.92   5.705%   $255.7215   $255.72   $255.70   $255.70  
  7 purchase totals = $1,121.98       $1,207.0322   $1,207.04   $1,206.95   $1,207.10