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 $86.46   11.184%   $96.1297   $96.13   $96.15   $96.10  
  Purchase #2 $158.56   7.547%   $170.5265   $170.53   $170.55   $170.50  
  Purchase #3 $224.70   6.843%   $240.0762   $240.08   $240.10   $240.10  
  Purchase #4 $249.79   7.164%   $267.685   $267.69   $267.70   $267.70  
  Purchase #5 $95.92   5.414%   $101.1131   $101.11   $101.10   $101.10  
  Purchase #6 $239.92   7.285%   $257.3982   $257.40   $257.40   $257.40  
  Purchase #7 $62.49   5.825%   $66.13   $66.13   $66.15   $66.10  
  7 purchase totals = $1,117.84       $1,199.0587   $1,199.07   $1,199.15   $1,199.00