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 $153.79   7.450%   $165.2474   $165.25   $165.25   $165.20  
  Purchase #2 $208.62   13.867%   $237.5493   $237.55   $237.55   $237.50  
  Purchase #3 $56.90   12.211%   $63.8481   $63.85   $63.85   $63.80  
  Purchase #4 $232.38   5.221%   $244.5126   $244.51   $244.50   $244.50  
  Purchase #5 $241.60   4.683%   $252.9141   $252.91   $252.90   $252.90  
  Purchase #6 $121.70   11.410%   $135.586   $135.59   $135.60   $135.60  
  Purchase #7 $106.69   11.148%   $118.5838   $118.58   $118.60   $118.60  
  7 purchase totals = $1,121.68       $1,218.2413   $1,218.24   $1,218.25   $1,218.10