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 $62.81   4.687%   $65.7539   $65.75   $65.75   $65.80  
  Purchase #2 $207.77   13.592%   $236.0101   $236.01   $236.00   $236.00  
  Purchase #3 $103.73   8.699%   $112.7535   $112.75   $112.75   $112.80  
  Purchase #4 $163.75   11.213%   $182.1113   $182.11   $182.10   $182.10  
  Purchase #5 $126.69   7.195%   $135.8053   $135.81   $135.80   $135.80  
  Purchase #6 $171.70   7.826%   $185.1372   $185.14   $185.15   $185.10  
  Purchase #7 $100.35   4.833%   $105.1999   $105.20   $105.20   $105.20  
  7 purchase totals = $936.80       $1,022.7712   $1,022.77   $1,022.75   $1,022.80