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 $203.67   3.615%   $211.0327   $211.03   $211.05   $211.00  
  Purchase #2 $6.95   7.168%   $7.4482   $7.45   $7.45   $7.40  
  Purchase #3 $174.68   11.776%   $195.2503   $195.25   $195.25   $195.30  
  Purchase #4 $216.94   4.470%   $226.6372   $226.64   $226.65   $226.60  
  Purchase #5 $95.53   11.549%   $106.5628   $106.56   $106.55   $106.60  
  Purchase #6 $149.79   7.750%   $161.3987   $161.40   $161.40   $161.40  
  Purchase #7 $39.98   3.246%   $41.2778   $41.28   $41.30   $41.30  
  7 purchase totals = $887.54       $949.6077   $949.61   $949.65   $949.60