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 $194.45   6.285%   $206.6712   $206.67   $206.65   $206.70  
  Purchase #2 $56.42   4.323%   $58.859   $58.86   $58.85   $58.90  
  Purchase #3 $182.69   3.212%   $188.558   $188.56   $188.55   $188.60  
  Purchase #4 $160.75   8.652%   $174.6581   $174.66   $174.65   $174.70  
  Purchase #5 $178.45   6.260%   $189.621   $189.62   $189.60   $189.60  
  Purchase #6 $206.99   9.645%   $226.9542   $226.95   $226.95   $227.00  
  Purchase #7 $231.86   13.143%   $262.3334   $262.33   $262.35   $262.30  
  7 purchase totals = $1,211.61       $1,307.6549   $1,307.65   $1,307.60   $1,307.80