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 $166.75   10.321%   $183.9603   $183.96   $183.95   $184.00  
  Purchase #2 $63.33   3.690%   $65.6669   $65.67   $65.65   $65.70  
  Purchase #3 $246.85   6.395%   $262.6361   $262.64   $262.65   $262.60  
  Purchase #4 $139.51   12.680%   $157.1999   $157.20   $157.20   $157.20  
  Purchase #5 $22.39   7.855%   $24.1487   $24.15   $24.15   $24.10  
  Purchase #6 $59.47   7.858%   $64.1432   $64.14   $64.15   $64.10  
  Purchase #7 $177.57   10.517%   $196.245   $196.25   $196.25   $196.20  
  7 purchase totals = $875.87       $954.0001   $954.01   $954.00   $953.90