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 $214.94   8.784%   $233.8203   $233.82   $233.80   $233.80  
  Purchase #2 $207.66   10.494%   $229.4518   $229.45   $229.45   $229.50  
  Purchase #3 $90.93   3.577%   $94.1826   $94.18   $94.20   $94.20  
  Purchase #4 $159.79   5.193%   $168.0879   $168.09   $168.10   $168.10  
  Purchase #5 $191.29   6.591%   $203.8979   $203.90   $203.90   $203.90  
  Purchase #6 $64.48   12.175%   $72.3304   $72.33   $72.35   $72.30  
  Purchase #7 $208.30   12.547%   $234.4354   $234.44   $234.45   $234.40  
  7 purchase totals = $1,137.39       $1,236.2063   $1,236.21   $1,236.25   $1,236.20