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 $86.79   9.420%   $94.9656   $94.97   $94.95   $95.00  
  Purchase #2 $113.65   8.352%   $123.142   $123.14   $123.15   $123.10  
  Purchase #3 $186.39   6.467%   $198.4438   $198.44   $198.45   $198.40  
  Purchase #4 $125.88   12.333%   $141.4048   $141.40   $141.40   $141.40  
  Purchase #5 $120.62   9.671%   $132.2852   $132.29   $132.30   $132.30  
  Purchase #6 $152.85   13.422%   $173.3655   $173.37   $173.35   $173.40  
  Purchase #7 $8.79   5.344%   $9.2597   $9.26   $9.25   $9.30  
  7 purchase totals = $794.97       $872.8666   $872.87   $872.85   $872.90