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 $35.34   7.555%   $38.0099   $38.01   $38.00   $38.00  
  Purchase #2 $178.78   12.250%   $200.6806   $200.68   $200.70   $200.70  
  Purchase #3 $207.54   10.248%   $228.8087   $228.81   $228.80   $228.80  
  Purchase #4 $194.94   3.269%   $201.3126   $201.31   $201.30   $201.30  
  Purchase #5 $25.33   3.786%   $26.289   $26.29   $26.30   $26.30  
  Purchase #6 $186.86   12.617%   $210.4361   $210.44   $210.45   $210.40  
  Purchase #7 $107.28   3.156%   $110.6658   $110.67   $110.65   $110.70  
  7 purchase totals = $936.07       $1,016.2027   $1,016.21   $1,016.20   $1,016.20