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 $118.63   5.810%   $125.5224   $125.52   $125.50   $125.50  
  Purchase #2 $232.62   6.540%   $247.8333   $247.83   $247.85   $247.80  
  Purchase #3 $17.82   12.619%   $20.0687   $20.07   $20.05   $20.10  
  Purchase #4 $149.79   9.286%   $163.6995   $163.70   $163.70   $163.70  
  Purchase #5 $220.69   5.794%   $233.4768   $233.48   $233.50   $233.50  
  Purchase #6 $167.73   13.759%   $190.808   $190.81   $190.80   $190.80  
  Purchase #7 $173.82   13.670%   $197.5812   $197.58   $197.60   $197.60  
  7 purchase totals = $1,081.10       $1,178.9899   $1,178.99   $1,179.00   $1,179.00