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 $54.49   7.330%   $58.4841   $58.48   $58.50   $58.50  
  Purchase #2 $237.65   6.176%   $252.3273   $252.33   $252.35   $252.30  
  Purchase #3 $112.30   12.242%   $126.0478   $126.05   $126.05   $126.00  
  Purchase #4 $89.72   13.198%   $101.5612   $101.56   $101.55   $101.60  
  Purchase #5 $235.79   13.873%   $268.5011   $268.50   $268.50   $268.50  
  Purchase #6 $222.78   5.865%   $235.846   $235.85   $235.85   $235.80  
  Purchase #7 $152.55   8.604%   $165.6754   $165.68   $165.70   $165.70  
  7 purchase totals = $1,105.28       $1,208.4429   $1,208.45   $1,208.50   $1,208.40