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 $119.98   5.839%   $126.9856   $126.99   $127.00   $127.00  
  Purchase #2 $160.83   3.814%   $166.9641   $166.96   $166.95   $167.00  
  Purchase #3 $212.69   4.402%   $222.0526   $222.05   $222.05   $222.10  
  Purchase #4 $29.35   8.738%   $31.9146   $31.91   $31.90   $31.90  
  Purchase #5 $131.65   3.783%   $136.6303   $136.63   $136.65   $136.60  
  Purchase #6 $128.56   3.564%   $133.1419   $133.14   $133.15   $133.10  
  Purchase #7 $54.51   6.153%   $57.864   $57.86   $57.85   $57.90  
  7 purchase totals = $837.57       $875.5531   $875.54   $875.55   $875.60