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 $104.98   9.323%   $114.7673   $114.77   $114.75   $114.80  
  Purchase #2 $228.56   6.139%   $242.5913   $242.59   $242.60   $242.60  
  Purchase #3 $176.99   13.266%   $200.4695   $200.47   $200.45   $200.50  
  Purchase #4 $49.85   8.357%   $54.016   $54.02   $54.00   $54.00  
  Purchase #5 $189.59   3.208%   $195.672   $195.67   $195.65   $195.70  
  Purchase #6 $174.99   8.337%   $189.5789   $189.58   $189.60   $189.60  
  Purchase #7 $148.64   11.694%   $166.022   $166.02   $166.00   $166.00  
  7 purchase totals = $1,073.60       $1,163.1170   $1,163.12   $1,163.05   $1,163.20