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 $102.76   11.844%   $114.9309   $114.93   $114.95   $114.90  
  Purchase #2 $250.97   6.144%   $266.3896   $266.39   $266.40   $266.40  
  Purchase #3 $72.44   11.600%   $80.843   $80.84   $80.85   $80.80  
  Purchase #4 $167.95   5.549%   $177.2695   $177.27   $177.25   $177.30  
  Purchase #5 $145.59   11.867%   $162.8672   $162.87   $162.85   $162.90  
  Purchase #6 $121.68   7.327%   $130.5955   $130.60   $130.60   $130.60  
  Purchase #7 $153.45   4.412%   $160.2202   $160.22   $160.20   $160.20  
  7 purchase totals = $1,014.84       $1,093.1159   $1,093.12   $1,093.10   $1,093.10