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 $71.34   7.867%   $76.9523   $76.95   $76.95   $77.00  
  Purchase #2 $104.78   13.657%   $119.0898   $119.09   $119.10   $119.10  
  Purchase #3 $122.36   4.304%   $127.6264   $127.63   $127.65   $127.60  
  Purchase #4 $146.87   9.371%   $160.6332   $160.63   $160.65   $160.60  
  Purchase #5 $152.30   9.112%   $166.1776   $166.18   $166.20   $166.20  
  Purchase #6 $166.92   12.631%   $188.0037   $188.00   $188.00   $188.00  
  Purchase #7 $205.67   12.703%   $231.7963   $231.80   $231.80   $231.80  
  7 purchase totals = $970.24       $1,070.2793   $1,070.28   $1,070.35   $1,070.30