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 $195.90   6.610%   $208.849   $208.85   $208.85   $208.80  
  Purchase #2 $53.70   7.180%   $57.5557   $57.56   $57.55   $57.60  
  Purchase #3 $228.80   4.589%   $239.2996   $239.30   $239.30   $239.30  
  Purchase #4 $144.49   6.445%   $153.8024   $153.80   $153.80   $153.80  
  Purchase #5 $105.33   11.150%   $117.0743   $117.07   $117.05   $117.10  
  Purchase #6 $211.37   5.570%   $223.1433   $223.14   $223.15   $223.10  
  Purchase #7 $170.53   13.413%   $193.4032   $193.40   $193.40   $193.40  
  7 purchase totals = $1,110.12       $1,193.1275   $1,193.12   $1,193.10   $1,193.10