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 $41.77   11.415%   $46.538   $46.54   $46.55   $46.50  
  Purchase #2 $210.33   7.509%   $226.1237   $226.12   $226.10   $226.10  
  Purchase #3 $146.62   12.417%   $164.8258   $164.83   $164.85   $164.80  
  Purchase #4 $71.34   6.153%   $75.7296   $75.73   $75.75   $75.70  
  Purchase #5 $206.42   3.215%   $213.0564   $213.06   $213.05   $213.10  
  Purchase #6 $228.73   5.722%   $241.8179   $241.82   $241.80   $241.80  
  Purchase #7 $180.68   11.695%   $201.8105   $201.81   $201.80   $201.80  
  7 purchase totals = $1,085.89       $1,169.9019   $1,169.91   $1,169.90   $1,169.80