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 $153.82   6.479%   $163.786   $163.79   $163.80   $163.80  
  Purchase #2 $88.27   8.409%   $95.6926   $95.69   $95.70   $95.70  
  Purchase #3 $57.37   6.643%   $61.1811   $61.18   $61.20   $61.20  
  Purchase #4 $84.94   12.297%   $95.3851   $95.39   $95.40   $95.40  
  Purchase #5 $239.85   4.835%   $251.4467   $251.45   $251.45   $251.40  
  Purchase #6 $97.45   8.539%   $105.7713   $105.77   $105.75   $105.80  
  Purchase #7 $227.36   10.287%   $250.7485   $250.75   $250.75   $250.70  
  7 purchase totals = $949.06       $1,024.0113   $1,024.02   $1,024.05   $1,024.00