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 $95.84   10.625%   $106.023   $106.02   $106.00   $106.00  
  Purchase #2 $236.55   12.173%   $265.3452   $265.35   $265.35   $265.30  
  Purchase #3 $73.96   4.385%   $77.2031   $77.20   $77.20   $77.20  
  Purchase #4 $175.59   6.122%   $186.3396   $186.34   $186.35   $186.30  
  Purchase #5 $74.58   12.487%   $83.8928   $83.89   $83.90   $83.90  
  Purchase #6 $15.48   8.630%   $16.8159   $16.82   $16.80   $16.80  
  Purchase #7 $238.64   5.705%   $252.2544   $252.25   $252.25   $252.30  
  7 purchase totals = $910.64       $987.8740   $987.87   $987.85   $987.80