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 $90.55   5.675%   $95.6887   $95.69   $95.70   $95.70  
  Purchase #2 $215.90   8.575%   $234.4134   $234.41   $234.40   $234.40  
  Purchase #3 $135.60   10.283%   $149.5437   $149.54   $149.55   $149.50  
  Purchase #4 $66.62   8.332%   $72.1708   $72.17   $72.15   $72.20  
  Purchase #5 $148.32   12.122%   $166.2994   $166.30   $166.30   $166.30  
  Purchase #6 $203.59   6.391%   $216.6014   $216.60   $216.60   $216.60  
  Purchase #7 $150.90   5.112%   $158.614   $158.61   $158.60   $158.60  
  7 purchase totals = $1,011.48       $1,093.3314   $1,093.32   $1,093.30   $1,093.30