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 $87.61   10.703%   $96.9869   $96.99   $97.00   $97.00  
  Purchase #2 $215.31   4.522%   $225.0463   $225.05   $225.05   $225.00  
  Purchase #3 $14.44   5.248%   $15.1978   $15.20   $15.20   $15.20  
  Purchase #4 $240.38   10.613%   $265.8915   $265.89   $265.90   $265.90  
  Purchase #5 $141.85   10.187%   $156.3003   $156.30   $156.30   $156.30  
  Purchase #6 $225.37   9.618%   $247.0461   $247.05   $247.05   $247.00  
  Purchase #7 $213.81   3.453%   $221.1929   $221.19   $221.20   $221.20  
  7 purchase totals = $1,138.77       $1,227.6618   $1,227.67   $1,227.70   $1,227.60