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 $96.56   8.255%   $104.531   $104.53   $104.55   $104.50  
  Purchase #2 $88.59   4.619%   $92.682   $92.68   $92.70   $92.70  
  Purchase #3 $248.33   7.266%   $266.3737   $266.37   $266.35   $266.40  
  Purchase #4 $243.59   3.421%   $251.9232   $251.92   $251.90   $251.90  
  Purchase #5 $151.76   3.486%   $157.0504   $157.05   $157.05   $157.10  
  Purchase #6 $90.31   6.529%   $96.2063   $96.21   $96.20   $96.20  
  Purchase #7 $187.88   13.305%   $212.8774   $212.88   $212.90   $212.90  
  7 purchase totals = $1,107.02       $1,181.6440   $1,181.64   $1,181.65   $1,181.70