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 $226.98   3.511%   $234.9493   $234.95   $234.95   $234.90  
  Purchase #2 $19.87   8.222%   $21.5037   $21.50   $21.50   $21.50  
  Purchase #3 $86.36   9.342%   $94.4278   $94.43   $94.45   $94.40  
  Purchase #4 $184.74   5.861%   $195.5676   $195.57   $195.55   $195.60  
  Purchase #5 $228.32   11.287%   $254.0905   $254.09   $254.10   $254.10  
  Purchase #6 $161.89   9.783%   $177.7277   $177.73   $177.75   $177.70  
  Purchase #7 $166.41   5.446%   $175.4727   $175.47   $175.45   $175.50  
  7 purchase totals = $1,074.57       $1,153.7393   $1,153.74   $1,153.75   $1,153.70