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 $59.51   5.561%   $62.8194   $62.82   $62.80   $62.80  
  Purchase #2 $122.80   9.200%   $134.0976   $134.10   $134.10   $134.10  
  Purchase #3 $133.59   9.515%   $146.3011   $146.30   $146.30   $146.30  
  Purchase #4 $233.49   11.166%   $259.5615   $259.56   $259.55   $259.60  
  Purchase #5 $180.80   11.402%   $201.4148   $201.41   $201.40   $201.40  
  Purchase #6 $117.47   9.629%   $128.7812   $128.78   $128.80   $128.80  
  Purchase #7 $57.68   8.147%   $62.3792   $62.38   $62.40   $62.40  
  7 purchase totals = $905.34       $995.3548   $995.35   $995.35   $995.40