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 $182.48   6.172%   $193.7427   $193.74   $193.75   $193.70  
  Purchase #2 $156.68   10.752%   $173.5262   $173.53   $173.55   $173.50  
  Purchase #3 $44.41   6.676%   $47.3748   $47.37   $47.35   $47.40  
  Purchase #4 $204.69   10.629%   $226.4465   $226.45   $226.45   $226.40  
  Purchase #5 $205.64   8.227%   $222.558   $222.56   $222.55   $222.60  
  Purchase #6 $203.64   5.352%   $214.5388   $214.54   $214.55   $214.50  
  Purchase #7 $15.55   9.755%   $17.0669   $17.07   $17.05   $17.10  
  7 purchase totals = $1,013.09       $1,095.2539   $1,095.26   $1,095.25   $1,095.20