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 $62.93   6.696%   $67.1438   $67.14   $67.15   $67.10  
  Purchase #2 $92.91   3.397%   $96.0662   $96.07   $96.05   $96.10  
  Purchase #3 $213.73   10.123%   $235.3659   $235.37   $235.35   $235.40  
  Purchase #4 $32.48   3.546%   $33.6317   $33.63   $33.65   $33.60  
  Purchase #5 $116.53   7.666%   $125.4632   $125.46   $125.45   $125.50  
  Purchase #6 $193.35   9.624%   $211.958   $211.96   $211.95   $212.00  
  Purchase #7 $166.29   11.533%   $185.4682   $185.47   $185.45   $185.50  
  7 purchase totals = $878.22       $955.0970   $955.10   $955.05   $955.20