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 $176.73   11.673%   $197.3597   $197.36   $197.35   $197.40  
  Purchase #2 $248.81   4.773%   $260.6857   $260.69   $260.70   $260.70  
  Purchase #3 $43.74   9.715%   $47.9893   $47.99   $48.00   $48.00  
  Purchase #4 $40.28   10.415%   $44.4752   $44.48   $44.50   $44.50  
  Purchase #5 $175.58   4.669%   $183.7778   $183.78   $183.80   $183.80  
  Purchase #6 $198.60   8.122%   $214.7303   $214.73   $214.75   $214.70  
  Purchase #7 $166.74   5.742%   $176.3142   $176.31   $176.30   $176.30  
  7 purchase totals = $1,050.48       $1,125.3322   $1,125.34   $1,125.40   $1,125.40