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 $65.57   11.298%   $72.9781   $72.98   $73.00   $73.00  
  Purchase #2 $146.34   5.457%   $154.3258   $154.33   $154.35   $154.30  
  Purchase #3 $44.46   12.531%   $50.0313   $50.03   $50.05   $50.00  
  Purchase #4 $164.72   4.401%   $171.9693   $171.97   $171.95   $172.00  
  Purchase #5 $232.41   9.155%   $253.6871   $253.69   $253.70   $253.70  
  Purchase #6 $219.56   6.348%   $233.4977   $233.50   $233.50   $233.50  
  Purchase #7 $186.77   5.307%   $196.6819   $196.68   $196.70   $196.70  
  7 purchase totals = $1,059.83       $1,133.1712   $1,133.18   $1,133.25   $1,133.20