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 $62.47   11.817%   $69.8521   $69.85   $69.85   $69.90  
  Purchase #2 $22.28   3.236%   $23.001   $23.00   $23.00   $23.00  
  Purchase #3 $221.92   13.791%   $252.525   $252.53   $252.55   $252.50  
  Purchase #4 $191.58   3.723%   $198.7125   $198.71   $198.70   $198.70  
  Purchase #5 $141.39   9.372%   $154.6411   $154.64   $154.65   $154.60  
  Purchase #6 $70.67   9.365%   $77.2882   $77.29   $77.30   $77.30  
  Purchase #7 $170.66   11.427%   $190.1613   $190.16   $190.15   $190.20  
  7 purchase totals = $880.97       $966.1812   $966.18   $966.20   $966.20