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 $154.54   5.257%   $162.6642   $162.66   $162.65   $162.70  
  Purchase #2 $119.39   3.744%   $123.86   $123.86   $123.85   $123.90  
  Purchase #3 $229.42   6.147%   $243.5224   $243.52   $243.50   $243.50  
  Purchase #4 $160.87   9.541%   $176.2186   $176.22   $176.20   $176.20  
  Purchase #5 $240.49   7.126%   $257.6273   $257.63   $257.65   $257.60  
  Purchase #6 $61.67   3.634%   $63.9111   $63.91   $63.90   $63.90  
  Purchase #7 $234.64   4.435%   $245.0463   $245.05   $245.05   $245.00  
  7 purchase totals = $1,201.02       $1,272.8499   $1,272.85   $1,272.80   $1,272.80