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 $35.94   5.789%   $38.0206   $38.02   $38.00   $38.00  
  Purchase #2 $211.95   3.839%   $220.0868   $220.09   $220.10   $220.10  
  Purchase #3 $19.78   5.627%   $20.893   $20.89   $20.90   $20.90  
  Purchase #4 $64.75   5.735%   $68.4634   $68.46   $68.45   $68.50  
  Purchase #5 $239.38   6.480%   $254.8918   $254.89   $254.90   $254.90  
  Purchase #6 $244.43   11.430%   $272.3683   $272.37   $272.35   $272.40  
  Purchase #7 $65.68   6.344%   $69.8467   $69.85   $69.85   $69.80  
  7 purchase totals = $881.91       $944.5706   $944.57   $944.55   $944.60