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 $213.27   4.678%   $223.2468   $223.25   $223.25   $223.20  
  Purchase #2 $190.58   8.504%   $206.7869   $206.79   $206.80   $206.80  
  Purchase #3 $248.88   7.550%   $267.6704   $267.67   $267.65   $267.70  
  Purchase #4 $250.77   4.213%   $261.3349   $261.33   $261.35   $261.30  
  Purchase #5 $235.60   6.279%   $250.3933   $250.39   $250.40   $250.40  
  Purchase #6 $212.73   10.656%   $235.3985   $235.40   $235.40   $235.40  
  Purchase #7 $60.27   3.508%   $62.3843   $62.38   $62.40   $62.40  
  7 purchase totals = $1,412.10       $1,507.2151   $1,507.21   $1,507.25   $1,507.20