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 $215.74   11.722%   $241.029   $241.03   $241.05   $241.00  
  Purchase #2 $193.36   6.598%   $206.1179   $206.12   $206.10   $206.10  
  Purchase #3 $23.75   5.860%   $25.1418   $25.14   $25.15   $25.10  
  Purchase #4 $130.68   5.172%   $137.4388   $137.44   $137.45   $137.40  
  Purchase #5 $234.66   13.826%   $267.1041   $267.10   $267.10   $267.10  
  Purchase #6 $233.83   13.196%   $264.6862   $264.69   $264.70   $264.70  
  Purchase #7 $33.83   6.821%   $36.1375   $36.14   $36.15   $36.10  
  7 purchase totals = $1,065.85       $1,177.6553   $1,177.66   $1,177.70   $1,177.50