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 $125.75   11.475%   $140.1798   $140.18   $140.20   $140.20  
  Purchase #2 $231.41   7.439%   $248.6246   $248.62   $248.60   $248.60  
  Purchase #3 $119.43   5.749%   $126.296   $126.30   $126.30   $126.30  
  Purchase #4 $191.30   11.133%   $212.5974   $212.60   $212.60   $212.60  
  Purchase #5 $228.36   11.523%   $254.6739   $254.67   $254.65   $254.70  
  Purchase #6 $235.32   7.643%   $253.3055   $253.31   $253.30   $253.30  
  Purchase #7 $200.29   12.494%   $225.3142   $225.31   $225.30   $225.30  
  7 purchase totals = $1,331.86       $1,460.9914   $1,460.99   $1,460.95   $1,461.00