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 $200.69   5.374%   $211.4751   $211.48   $211.50   $211.50  
  Purchase #2 $208.57   5.798%   $220.6629   $220.66   $220.65   $220.70  
  Purchase #3 $119.92   4.363%   $125.1521   $125.15   $125.15   $125.20  
  Purchase #4 $56.45   12.419%   $63.4605   $63.46   $63.45   $63.50  
  Purchase #5 $175.75   11.357%   $195.7099   $195.71   $195.70   $195.70  
  Purchase #6 $42.28   3.694%   $43.8418   $43.84   $43.85   $43.80  
  Purchase #7 $145.45   5.677%   $153.7072   $153.71   $153.70   $153.70  
  7 purchase totals = $949.11       $1,014.0095   $1,014.01   $1,014.00   $1,014.10