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 $44.70   5.867%   $47.3225   $47.32   $47.30   $47.30  
  Purchase #2 $154.48   3.684%   $160.171   $160.17   $160.15   $160.20  
  Purchase #3 $205.37   13.187%   $232.4521   $232.45   $232.45   $232.50  
  Purchase #4 $74.31   3.489%   $76.9027   $76.90   $76.90   $76.90  
  Purchase #5 $147.27   8.104%   $159.2048   $159.20   $159.20   $159.20  
  Purchase #6 $240.71   13.439%   $273.059   $273.06   $273.05   $273.10  
  Purchase #7 $67.89   9.667%   $74.4529   $74.45   $74.45   $74.50  
  7 purchase totals = $934.73       $1,023.5650   $1,023.55   $1,023.50   $1,023.70