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 $173.97   13.187%   $196.9114   $196.91   $196.90   $196.90  
  Purchase #2 $215.75   4.295%   $225.0165   $225.02   $225.00   $225.00  
  Purchase #3 $148.46   5.696%   $156.9163   $156.92   $156.90   $156.90  
  Purchase #4 $161.38   5.720%   $170.6109   $170.61   $170.60   $170.60  
  Purchase #5 $23.69   7.750%   $25.526   $25.53   $25.55   $25.50  
  Purchase #6 $60.35   6.127%   $64.0476   $64.05   $64.05   $64.00  
  Purchase #7 $177.77   3.771%   $184.4737   $184.47   $184.45   $184.50  
  7 purchase totals = $961.37       $1,023.5024   $1,023.51   $1,023.45   $1,023.40