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 $57.31   8.515%   $62.1899   $62.19   $62.20   $62.20  
  Purchase #2 $10.29   8.435%   $11.158   $11.16   $11.15   $11.20  
  Purchase #3 $201.72   4.455%   $210.7066   $210.71   $210.70   $210.70  
  Purchase #4 $177.39   11.804%   $198.3291   $198.33   $198.35   $198.30  
  Purchase #5 $89.37   13.539%   $101.4698   $101.47   $101.45   $101.50  
  Purchase #6 $242.99   12.868%   $274.258   $274.26   $274.25   $274.30  
  Purchase #7 $209.44   13.360%   $237.4212   $237.42   $237.40   $237.40  
  7 purchase totals = $988.51       $1,095.5326   $1,095.54   $1,095.50   $1,095.60