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 $119.61   5.190%   $125.8178   $125.82   $125.80   $125.80  
  Purchase #2 $206.47   6.873%   $220.6607   $220.66   $220.65   $220.70  
  Purchase #3 $247.64   11.676%   $276.5544   $276.55   $276.55   $276.60  
  Purchase #4 $197.80   3.675%   $205.0692   $205.07   $205.05   $205.10  
  Purchase #5 $182.43   11.462%   $203.3401   $203.34   $203.35   $203.30  
  Purchase #6 $144.79   3.122%   $149.3103   $149.31   $149.30   $149.30  
  Purchase #7 $83.89   13.768%   $95.44   $95.44   $95.45   $95.40  
  7 purchase totals = $1,182.63       $1,276.1925   $1,276.19   $1,276.15   $1,276.20