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 $119.95   4.475%   $125.3178   $125.32   $125.30   $125.30  
  Purchase #2 $234.67   13.502%   $266.3551   $266.36   $266.35   $266.40  
  Purchase #3 $145.81   6.511%   $155.3037   $155.30   $155.30   $155.30  
  Purchase #4 $142.78   13.443%   $161.9739   $161.97   $161.95   $162.00  
  Purchase #5 $117.27   6.441%   $124.8234   $124.82   $124.80   $124.80  
  Purchase #6 $206.63   4.833%   $216.6164   $216.62   $216.60   $216.60  
  Purchase #7 $196.75   3.154%   $202.9555   $202.96   $202.95   $203.00  
  7 purchase totals = $1,163.86       $1,253.3458   $1,253.35   $1,253.25   $1,253.40