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 $130.94   8.103%   $141.5501   $141.55   $141.55   $141.60  
  Purchase #2 $212.42   8.452%   $230.3737   $230.37   $230.35   $230.40  
  Purchase #3 $236.95   4.291%   $247.1175   $247.12   $247.10   $247.10  
  Purchase #4 $87.48   13.738%   $99.498   $99.50   $99.50   $99.50  
  Purchase #5 $93.88   12.319%   $105.4451   $105.45   $105.45   $105.40  
  Purchase #6 $25.92   3.606%   $26.8547   $26.85   $26.85   $26.90  
  Purchase #7 $111.99   3.648%   $116.0754   $116.08   $116.10   $116.10  
  7 purchase totals = $899.58       $966.9145   $966.92   $966.90   $967.00