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 $171.44   13.474%   $194.5398   $194.54   $194.55   $194.50  
  Purchase #2 $215.73   3.196%   $222.6247   $222.62   $222.60   $222.60  
  Purchase #3 $60.27   9.494%   $65.992   $65.99   $66.00   $66.00  
  Purchase #4 $144.66   12.555%   $162.8221   $162.82   $162.80   $162.80  
  Purchase #5 $249.46   13.431%   $282.965   $282.97   $282.95   $283.00  
  Purchase #6 $235.88   10.864%   $261.506   $261.51   $261.50   $261.50  
  Purchase #7 $53.66   6.168%   $56.9697   $56.97   $56.95   $57.00  
  7 purchase totals = $1,131.10       $1,247.4193   $1,247.42   $1,247.35   $1,247.40