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 $108.58   5.697%   $114.7658   $114.77   $114.75   $114.80  
  Purchase #2 $22.90   12.241%   $25.7032   $25.70   $25.70   $25.70  
  Purchase #3 $162.32   13.807%   $184.7315   $184.73   $184.75   $184.70  
  Purchase #4 $39.86   11.560%   $44.4678   $44.47   $44.45   $44.50  
  Purchase #5 $177.69   8.728%   $193.1988   $193.20   $193.20   $193.20  
  Purchase #6 $239.97   7.241%   $257.3462   $257.35   $257.35   $257.30  
  Purchase #7 $222.38   4.826%   $233.1121   $233.11   $233.10   $233.10  
  7 purchase totals = $973.70       $1,053.3254   $1,053.33   $1,053.30   $1,053.30