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 $174.26   11.333%   $194.0089   $194.01   $194.00   $194.00  
  Purchase #2 $78.63   7.568%   $84.5807   $84.58   $84.60   $84.60  
  Purchase #3 $11.31   5.548%   $11.9375   $11.94   $11.95   $11.90  
  Purchase #4 $248.71   9.602%   $272.5911   $272.59   $272.60   $272.60  
  Purchase #5 $247.34   7.338%   $265.4898   $265.49   $265.50   $265.50  
  Purchase #6 $230.42   6.709%   $245.8789   $245.88   $245.90   $245.90  
  Purchase #7 $102.71   3.677%   $106.4866   $106.49   $106.50   $106.50  
  7 purchase totals = $1,093.38       $1,180.9735   $1,180.98   $1,181.05   $1,181.00