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 $157.58   8.634%   $171.1855   $171.19   $171.20   $171.20  
  Purchase #2 $245.80   6.593%   $262.0056   $262.01   $262.00   $262.00  
  Purchase #3 $215.50   13.793%   $245.2239   $245.22   $245.20   $245.20  
  Purchase #4 $137.44   4.447%   $143.552   $143.55   $143.55   $143.60  
  Purchase #5 $156.62   8.737%   $170.3039   $170.30   $170.30   $170.30  
  Purchase #6 $67.89   13.759%   $77.231   $77.23   $77.25   $77.20  
  Purchase #7 $114.44   9.669%   $125.5052   $125.51   $125.50   $125.50  
  7 purchase totals = $1,095.27       $1,195.0071   $1,195.01   $1,195.00   $1,195.00