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 $58.61   6.733%   $62.5562   $62.56   $62.55   $62.60  
  Purchase #2 $67.68   5.147%   $71.1635   $71.16   $71.15   $71.20  
  Purchase #3 $224.70   9.129%   $245.2129   $245.21   $245.20   $245.20  
  Purchase #4 $57.90   5.294%   $60.9652   $60.97   $60.95   $61.00  
  Purchase #5 $90.48   3.503%   $93.6495   $93.65   $93.65   $93.60  
  Purchase #6 $147.49   11.446%   $164.3717   $164.37   $164.35   $164.40  
  Purchase #7 $228.81   11.183%   $254.3978   $254.40   $254.40   $254.40  
  7 purchase totals = $875.67       $952.3168   $952.32   $952.25   $952.40