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 $58.39   7.163%   $62.5725   $62.57   $62.55   $62.60  
  Purchase #2 $137.64   6.374%   $146.4132   $146.41   $146.40   $146.40  
  Purchase #3 $142.59   13.811%   $162.2831   $162.28   $162.30   $162.30  
  Purchase #4 $240.69   13.705%   $273.6766   $273.68   $273.70   $273.70  
  Purchase #5 $220.35   9.578%   $241.4551   $241.46   $241.45   $241.50  
  Purchase #6 $26.73   4.361%   $27.8957   $27.90   $27.90   $27.90  
  Purchase #7 $170.47   12.678%   $192.0822   $192.08   $192.10   $192.10  
  7 purchase totals = $996.86       $1,106.3784   $1,106.38   $1,106.40   $1,106.50