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 $114.51   9.241%   $125.0919   $125.09   $125.10   $125.10  
  Purchase #2 $197.38   6.236%   $209.6886   $209.69   $209.70   $209.70  
  Purchase #3 $184.68   5.115%   $194.1264   $194.13   $194.15   $194.10  
  Purchase #4 $211.59   9.357%   $231.3885   $231.39   $231.40   $231.40  
  Purchase #5 $193.95   10.461%   $214.2391   $214.24   $214.25   $214.20  
  Purchase #6 $171.98   8.707%   $186.9543   $186.95   $186.95   $187.00  
  Purchase #7 $43.78   8.502%   $47.5022   $47.50   $47.50   $47.50  
  7 purchase totals = $1,117.87       $1,208.9910   $1,208.99   $1,209.05   $1,209.00