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 $229.79   13.849%   $261.6136   $261.61   $261.60   $261.60  
  Purchase #2 $169.34   10.476%   $187.0801   $187.08   $187.10   $187.10  
  Purchase #3 $98.60   3.205%   $101.7601   $101.76   $101.75   $101.80  
  Purchase #4 $135.84   9.346%   $148.5356   $148.54   $148.55   $148.50  
  Purchase #5 $37.28   11.703%   $41.6429   $41.64   $41.65   $41.60  
  Purchase #6 $200.29   13.176%   $226.6802   $226.68   $226.70   $226.70  
  Purchase #7 $154.62   8.267%   $167.4024   $167.40   $167.40   $167.40  
  7 purchase totals = $1,025.76       $1,134.7149   $1,134.71   $1,134.75   $1,134.70