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 $176.71   10.486%   $195.2398   $195.24   $195.25   $195.20  
  Purchase #2 $225.74   10.723%   $249.9461   $249.95   $249.95   $249.90  
  Purchase #3 $33.81   3.391%   $34.9565   $34.96   $34.95   $35.00  
  Purchase #4 $192.54   7.413%   $206.813   $206.81   $206.80   $206.80  
  Purchase #5 $204.40   4.797%   $214.2051   $214.21   $214.20   $214.20  
  Purchase #6 $126.30   9.854%   $138.7456   $138.75   $138.75   $138.70  
  Purchase #7 $192.56   13.337%   $218.2417   $218.24   $218.25   $218.20  
  7 purchase totals = $1,152.06       $1,258.1478   $1,258.16   $1,258.15   $1,258.00