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 $182.43   7.418%   $195.9627   $195.96   $195.95   $196.00  
  Purchase #2 $27.37   8.123%   $29.5933   $29.59   $29.60   $29.60  
  Purchase #3 $142.68   6.141%   $151.442   $151.44   $151.45   $151.40  
  Purchase #4 $235.75   5.577%   $248.8978   $248.90   $248.90   $248.90  
  Purchase #5 $207.45   5.787%   $219.4551   $219.46   $219.45   $219.50  
  Purchase #6 $205.75   6.222%   $218.5518   $218.55   $218.55   $218.60  
  Purchase #7 $137.87   9.775%   $151.3468   $151.35   $151.35   $151.30  
  7 purchase totals = $1,139.30       $1,215.2495   $1,215.25   $1,215.25   $1,215.30