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 $235.27   11.681%   $262.7519   $262.75   $262.75   $262.80  
  Purchase #2 $155.74   10.171%   $171.5803   $171.58   $171.60   $171.60  
  Purchase #3 $113.63   9.260%   $124.1521   $124.15   $124.15   $124.20  
  Purchase #4 $96.75   4.750%   $101.3456   $101.35   $101.35   $101.30  
  Purchase #5 $6.76   12.281%   $7.5902   $7.59   $7.60   $7.60  
  Purchase #6 $236.68   12.761%   $266.8827   $266.88   $266.90   $266.90  
  Purchase #7 $76.59   6.674%   $81.7016   $81.70   $81.70   $81.70  
  7 purchase totals = $921.42       $1,016.0044   $1,016.00   $1,016.05   $1,016.10