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 $121.85   3.384%   $125.9734   $125.97   $125.95   $126.00  
  Purchase #2 $172.29   11.231%   $191.6399   $191.64   $191.65   $191.60  
  Purchase #3 $161.88   6.119%   $171.7854   $171.79   $171.80   $171.80  
  Purchase #4 $131.88   13.406%   $149.5598   $149.56   $149.55   $149.60  
  Purchase #5 $191.64   11.696%   $214.0542   $214.05   $214.05   $214.10  
  Purchase #6 $250.57   9.231%   $273.7001   $273.70   $273.70   $273.70  
  Purchase #7 $175.58   7.207%   $188.2341   $188.23   $188.25   $188.20  
  7 purchase totals = $1,205.69       $1,314.9469   $1,314.94   $1,314.95   $1,315.00