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 $60.38   4.737%   $63.2402   $63.24   $63.25   $63.20  
  Purchase #2 $12.27   7.127%   $13.1445   $13.14   $13.15   $13.10  
  Purchase #3 $240.76   4.148%   $250.7467   $250.75   $250.75   $250.70  
  Purchase #4 $184.48   7.802%   $198.8731   $198.87   $198.85   $198.90  
  Purchase #5 $132.85   9.643%   $145.6607   $145.66   $145.65   $145.70  
  Purchase #6 $206.26   6.786%   $220.2568   $220.26   $220.25   $220.30  
  Purchase #7 $156.77   3.188%   $161.7678   $161.77   $161.75   $161.80  
  7 purchase totals = $993.77       $1,053.6898   $1,053.69   $1,053.65   $1,053.70