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 $123.83   7.130%   $132.6591   $132.66   $132.65   $132.70  
  Purchase #2 $59.42   11.405%   $66.1969   $66.20   $66.20   $66.20  
  Purchase #3 $234.27   5.306%   $246.7004   $246.70   $246.70   $246.70  
  Purchase #4 $8.35   5.735%   $8.8289   $8.83   $8.85   $8.80  
  Purchase #5 $109.58   8.824%   $119.2493   $119.25   $119.25   $119.20  
  Purchase #6 $194.52   10.127%   $214.219   $214.22   $214.20   $214.20  
  Purchase #7 $152.90   7.404%   $164.2207   $164.22   $164.20   $164.20  
  7 purchase totals = $882.87       $952.0743   $952.08   $952.05   $952.00