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 $67.76   7.845%   $73.0758   $73.08   $73.10   $73.10  
  Purchase #2 $97.29   6.238%   $103.359   $103.36   $103.35   $103.40  
  Purchase #3 $77.95   10.830%   $86.392   $86.39   $86.40   $86.40  
  Purchase #4 $124.79   9.449%   $136.5814   $136.58   $136.60   $136.60  
  Purchase #5 $139.35   7.814%   $150.2388   $150.24   $150.25   $150.20  
  Purchase #6 $119.29   5.635%   $126.012   $126.01   $126.00   $126.00  
  Purchase #7 $195.99   6.212%   $208.1649   $208.16   $208.15   $208.20  
  7 purchase totals = $822.42       $883.8239   $883.82   $883.85   $883.90