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 $56.36   3.105%   $58.11   $58.11   $58.10   $58.10  
  Purchase #2 $148.55   5.470%   $156.6757   $156.68   $156.70   $156.70  
  Purchase #3 $148.58   11.203%   $165.2254   $165.23   $165.25   $165.20  
  Purchase #4 $230.68   10.227%   $254.2716   $254.27   $254.25   $254.30  
  Purchase #5 $220.78   9.719%   $242.2376   $242.24   $242.25   $242.20  
  Purchase #6 $216.36   12.388%   $243.1627   $243.16   $243.15   $243.20  
  Purchase #7 $245.58   8.673%   $266.8792   $266.88   $266.90   $266.90  
  7 purchase totals = $1,266.89       $1,386.5622   $1,386.57   $1,386.60   $1,386.60