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 $97.31   6.561%   $103.6945   $103.69   $103.70   $103.70  
  Purchase #2 $34.72   4.337%   $36.2258   $36.23   $36.25   $36.20  
  Purchase #3 $164.62   7.135%   $176.3656   $176.37   $176.35   $176.40  
  Purchase #4 $180.81   12.470%   $203.357   $203.36   $203.35   $203.40  
  Purchase #5 $170.41   3.616%   $176.572   $176.57   $176.55   $176.60  
  Purchase #6 $101.60   4.229%   $105.8967   $105.90   $105.90   $105.90  
  Purchase #7 $236.87   11.207%   $263.416   $263.42   $263.40   $263.40  
  7 purchase totals = $986.34       $1,065.5276   $1,065.54   $1,065.50   $1,065.60