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 $172.25   13.620%   $195.7105   $195.71   $195.70   $195.70  
  Purchase #2 $87.94   8.472%   $95.3903   $95.39   $95.40   $95.40  
  Purchase #3 $233.95   7.434%   $251.3418   $251.34   $251.35   $251.30  
  Purchase #4 $38.81   3.558%   $40.1909   $40.19   $40.20   $40.20  
  Purchase #5 $227.72   6.120%   $241.6565   $241.66   $241.65   $241.70  
  Purchase #6 $233.36   3.665%   $241.9126   $241.91   $241.90   $241.90  
  Purchase #7 $171.72   13.809%   $195.4328   $195.43   $195.45   $195.40  
  7 purchase totals = $1,165.75       $1,261.6354   $1,261.63   $1,261.65   $1,261.60