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 $60.95   5.240%   $64.1438   $64.14   $64.15   $64.10  
  Purchase #2 $221.75   10.776%   $245.6458   $245.65   $245.65   $245.60  
  Purchase #3 $178.89   12.352%   $200.9865   $200.99   $201.00   $201.00  
  Purchase #4 $177.96   4.464%   $185.9041   $185.90   $185.90   $185.90  
  Purchase #5 $89.48   6.852%   $95.6112   $95.61   $95.60   $95.60  
  Purchase #6 $204.55   9.356%   $223.6877   $223.69   $223.70   $223.70  
  Purchase #7 $15.58   13.584%   $17.6964   $17.70   $17.70   $17.70  
  7 purchase totals = $949.16       $1,033.6755   $1,033.68   $1,033.70   $1,033.60