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 $119.95   4.351%   $125.169   $125.17   $125.15   $125.20  
  Purchase #2 $62.57   5.116%   $65.7711   $65.77   $65.75   $65.80  
  Purchase #3 $229.59   4.470%   $239.8527   $239.85   $239.85   $239.90  
  Purchase #4 $63.47   3.544%   $65.7194   $65.72   $65.70   $65.70  
  Purchase #5 $182.48   10.129%   $200.9634   $200.96   $200.95   $201.00  
  Purchase #6 $165.30   5.253%   $173.9832   $173.98   $174.00   $174.00  
  Purchase #7 $201.29   12.160%   $225.7669   $225.77   $225.75   $225.80  
  7 purchase totals = $1,024.65       $1,097.2257   $1,097.22   $1,097.15   $1,097.40