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 $108.68   5.418%   $114.5683   $114.57   $114.55   $114.60  
  Purchase #2 $65.36   13.653%   $74.2836   $74.28   $74.30   $74.30  
  Purchase #3 $144.61   12.130%   $162.1512   $162.15   $162.15   $162.20  
  Purchase #4 $143.33   5.352%   $151.001   $151.00   $151.00   $151.00  
  Purchase #5 $66.42   10.798%   $73.592   $73.59   $73.60   $73.60  
  Purchase #6 $236.37   6.504%   $251.7435   $251.74   $251.75   $251.70  
  Purchase #7 $160.27   12.811%   $180.8022   $180.80   $180.80   $180.80  
  7 purchase totals = $925.04       $1,008.1418   $1,008.13   $1,008.15   $1,008.20