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 $45.32   7.562%   $48.7471   $48.75   $48.75   $48.70  
  Purchase #2 $248.97   9.798%   $273.3641   $273.36   $273.35   $273.40  
  Purchase #3 $195.49   3.106%   $201.5619   $201.56   $201.55   $201.60  
  Purchase #4 $172.36   11.150%   $191.5781   $191.58   $191.60   $191.60  
  Purchase #5 $146.56   10.370%   $161.7583   $161.76   $161.75   $161.80  
  Purchase #6 $14.86   3.495%   $15.3794   $15.38   $15.40   $15.40  
  Purchase #7 $141.95   12.441%   $159.61   $159.61   $159.60   $159.60  
  7 purchase totals = $965.51       $1,051.9989   $1,052.00   $1,052.00   $1,052.10