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 $59.30   4.764%   $62.1251   $62.13   $62.15   $62.10  
  Purchase #2 $195.95   11.216%   $217.9278   $217.93   $217.95   $217.90  
  Purchase #3 $14.30   13.256%   $16.1956   $16.20   $16.20   $16.20  
  Purchase #4 $84.69   11.433%   $94.3726   $94.37   $94.35   $94.40  
  Purchase #5 $139.72   13.835%   $159.0503   $159.05   $159.05   $159.10  
  Purchase #6 $191.70   11.675%   $214.081   $214.08   $214.10   $214.10  
  Purchase #7 $112.70   8.534%   $122.3178   $122.32   $122.30   $122.30  
  7 purchase totals = $798.36       $886.0702   $886.08   $886.10   $886.10