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 $23.35   9.692%   $25.6131   $25.61   $25.60   $25.60  
  Purchase #2 $67.99   10.307%   $74.9977   $75.00   $75.00   $75.00  
  Purchase #3 $210.81   11.229%   $234.4819   $234.48   $234.50   $234.50  
  Purchase #4 $186.98   5.224%   $196.7478   $196.75   $196.75   $196.70  
  Purchase #5 $166.97   13.721%   $189.88   $189.88   $189.90   $189.90  
  Purchase #6 $169.65   13.247%   $192.1235   $192.12   $192.10   $192.10  
  Purchase #7 $125.27   4.422%   $130.8094   $130.81   $130.80   $130.80  
  7 purchase totals = $951.02       $1,044.6534   $1,044.65   $1,044.65   $1,044.60