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 $77.48   9.247%   $84.6446   $84.64   $84.65   $84.60  
  Purchase #2 $158.41   10.284%   $174.7009   $174.70   $174.70   $174.70  
  Purchase #3 $91.28   9.213%   $99.6896   $99.69   $99.70   $99.70  
  Purchase #4 $207.44   9.164%   $226.4498   $226.45   $226.45   $226.40  
  Purchase #5 $88.49   10.549%   $97.8248   $97.82   $97.80   $97.80  
  Purchase #6 $236.36   12.282%   $265.3897   $265.39   $265.40   $265.40  
  Purchase #7 $151.27   8.240%   $163.7346   $163.73   $163.75   $163.70  
  7 purchase totals = $1,010.73       $1,112.4340   $1,112.42   $1,112.45   $1,112.30