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 $54.28   13.399%   $61.553   $61.55   $61.55   $61.60  
  Purchase #2 $161.56   10.530%   $178.5723   $178.57   $178.55   $178.60  
  Purchase #3 $224.40   7.399%   $241.0034   $241.00   $241.00   $241.00  
  Purchase #4 $222.40   10.143%   $244.958   $244.96   $244.95   $245.00  
  Purchase #5 $158.73   5.193%   $166.9728   $166.97   $166.95   $167.00  
  Purchase #6 $122.81   7.196%   $131.6474   $131.65   $131.65   $131.60  
  Purchase #7 $136.41   11.583%   $152.2104   $152.21   $152.20   $152.20  
  7 purchase totals = $1,080.59       $1,176.9173   $1,176.91   $1,176.85   $1,177.00