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 $72.82   4.541%   $76.1268   $76.13   $76.15   $76.10  
  Purchase #2 $179.63   5.633%   $189.7486   $189.75   $189.75   $189.70  
  Purchase #3 $227.58   11.873%   $254.6006   $254.60   $254.60   $254.60  
  Purchase #4 $191.37   5.868%   $202.5996   $202.60   $202.60   $202.60  
  Purchase #5 $140.74   11.243%   $156.5634   $156.56   $156.55   $156.60  
  Purchase #6 $56.64   12.437%   $63.6843   $63.68   $63.70   $63.70  
  Purchase #7 $125.87   5.672%   $133.0093   $133.01   $133.00   $133.00  
  7 purchase totals = $994.65       $1,076.3326   $1,076.33   $1,076.35   $1,076.30