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 $52.63   12.547%   $59.2335   $59.23   $59.25   $59.20  
  Purchase #2 $216.71   4.698%   $226.891   $226.89   $226.90   $226.90  
  Purchase #3 $33.45   5.716%   $35.362   $35.36   $35.35   $35.40  
  Purchase #4 $222.86   6.642%   $237.6624   $237.66   $237.65   $237.70  
  Purchase #5 $39.72   11.823%   $44.4161   $44.42   $44.40   $44.40  
  Purchase #6 $250.67   6.541%   $267.0663   $267.07   $267.05   $267.10  
  Purchase #7 $233.98   6.415%   $248.9898   $248.99   $249.00   $249.00  
  7 purchase totals = $1,050.02       $1,119.6211   $1,119.62   $1,119.60   $1,119.70