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 $219.59   5.773%   $232.2669   $232.27   $232.25   $232.30  
  Purchase #2 $209.27   3.656%   $216.9209   $216.92   $216.90   $216.90  
  Purchase #3 $117.85   13.333%   $133.5629   $133.56   $133.55   $133.60  
  Purchase #4 $86.69   13.228%   $98.1574   $98.16   $98.15   $98.20  
  Purchase #5 $63.35   9.702%   $69.4962   $69.50   $69.50   $69.50  
  Purchase #6 $37.96   11.125%   $42.1831   $42.18   $42.20   $42.20  
  Purchase #7 $150.91   7.153%   $161.7046   $161.70   $161.70   $161.70  
  7 purchase totals = $885.62       $954.2920   $954.29   $954.25   $954.40