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 $101.77   10.281%   $112.233   $112.23   $112.25   $112.20  
  Purchase #2 $24.50   6.451%   $26.0805   $26.08   $26.10   $26.10  
  Purchase #3 $87.80   11.147%   $97.5871   $97.59   $97.60   $97.60  
  Purchase #4 $48.78   10.833%   $54.0643   $54.06   $54.05   $54.10  
  Purchase #5 $166.87   9.110%   $182.0719   $182.07   $182.05   $182.10  
  Purchase #6 $208.35   8.612%   $226.2931   $226.29   $226.30   $226.30  
  Purchase #7 $85.61   13.689%   $97.3292   $97.33   $97.35   $97.30  
  7 purchase totals = $723.68       $795.6591   $795.65   $795.70   $795.70