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 $221.49   6.523%   $235.9378   $235.94   $235.95   $235.90  
  Purchase #2 $87.51   8.115%   $94.6114   $94.61   $94.60   $94.60  
  Purchase #3 $167.57   9.659%   $183.7556   $183.76   $183.75   $183.80  
  Purchase #4 $199.53   11.702%   $222.879   $222.88   $222.90   $222.90  
  Purchase #5 $68.25   4.799%   $71.5253   $71.53   $71.55   $71.50  
  Purchase #6 $211.59   11.602%   $236.1387   $236.14   $236.15   $236.10  
  Purchase #7 $190.80   6.520%   $203.2402   $203.24   $203.25   $203.20  
  7 purchase totals = $1,146.74       $1,248.0880   $1,248.10   $1,248.15   $1,248.00