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 $93.40   13.298%   $105.8203   $105.82   $105.80   $105.80  
  Purchase #2 $235.78   11.438%   $262.7485   $262.75   $262.75   $262.70  
  Purchase #3 $23.64   11.255%   $26.3007   $26.30   $26.30   $26.30  
  Purchase #4 $128.94   13.454%   $146.2876   $146.29   $146.30   $146.30  
  Purchase #5 $147.50   4.657%   $154.3691   $154.37   $154.35   $154.40  
  Purchase #6 $11.63   3.783%   $12.07   $12.07   $12.05   $12.10  
  Purchase #7 $112.70   5.336%   $118.7137   $118.71   $118.70   $118.70  
  7 purchase totals = $753.59       $826.3099   $826.31   $826.25   $826.30