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 $162.41   8.484%   $176.1889   $176.19   $176.20   $176.20  
  Purchase #2 $249.76   8.203%   $270.2478   $270.25   $270.25   $270.20  
  Purchase #3 $153.93   7.169%   $164.9652   $164.97   $164.95   $165.00  
  Purchase #4 $153.84   7.439%   $165.2842   $165.28   $165.30   $165.30  
  Purchase #5 $32.30   13.112%   $36.5352   $36.54   $36.55   $36.50  
  Purchase #6 $244.94   9.424%   $268.0231   $268.02   $268.00   $268.00  
  Purchase #7 $109.66   4.714%   $114.8294   $114.83   $114.85   $114.80  
  7 purchase totals = $1,106.84       $1,196.0738   $1,196.08   $1,196.10   $1,196.00