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 $23.91   8.668%   $25.9825   $25.98   $26.00   $26.00  
  Purchase #2 $236.88   4.415%   $247.3383   $247.34   $247.35   $247.30  
  Purchase #3 $68.97   8.491%   $74.8262   $74.83   $74.85   $74.80  
  Purchase #4 $178.91   13.851%   $203.6908   $203.69   $203.70   $203.70  
  Purchase #5 $171.71   12.456%   $193.0982   $193.10   $193.10   $193.10  
  Purchase #6 $213.94   13.778%   $243.4167   $243.42   $243.40   $243.40  
  Purchase #7 $100.67   12.571%   $113.3252   $113.33   $113.35   $113.30  
  7 purchase totals = $994.99       $1,101.6779   $1,101.69   $1,101.75   $1,101.60