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 $160.74   8.522%   $174.4383   $174.44   $174.45   $174.40  
  Purchase #2 $195.91   10.148%   $215.7909   $215.79   $215.80   $215.80  
  Purchase #3 $20.66   12.521%   $23.2468   $23.25   $23.25   $23.20  
  Purchase #4 $84.77   10.553%   $93.7158   $93.72   $93.70   $93.70  
  Purchase #5 $196.54   5.654%   $207.6524   $207.65   $207.65   $207.70  
  Purchase #6 $206.97   6.391%   $220.1975   $220.20   $220.20   $220.20  
  Purchase #7 $247.63   8.441%   $268.5324   $268.53   $268.55   $268.50  
  7 purchase totals = $1,113.22       $1,203.5741   $1,203.58   $1,203.60   $1,203.50