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 $132.75   6.725%   $141.6774   $141.68   $141.70   $141.70  
  Purchase #2 $173.28   12.746%   $195.3663   $195.37   $195.35   $195.40  
  Purchase #3 $168.48   3.866%   $174.9934   $174.99   $175.00   $175.00  
  Purchase #4 $120.25   3.348%   $124.276   $124.28   $124.30   $124.30  
  Purchase #5 $59.62   8.643%   $64.773   $64.77   $64.75   $64.80  
  Purchase #6 $9.92   10.775%   $10.9889   $10.99   $11.00   $11.00  
  Purchase #7 $194.46   3.215%   $200.7119   $200.71   $200.70   $200.70  
  7 purchase totals = $858.76       $912.7869   $912.79   $912.80   $912.90