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 $244.52   6.796%   $261.1376   $261.14   $261.15   $261.10  
  Purchase #2 $206.73   6.221%   $219.5907   $219.59   $219.60   $219.60  
  Purchase #3 $68.82   7.794%   $74.1838   $74.18   $74.20   $74.20  
  Purchase #4 $89.90   7.470%   $96.6155   $96.62   $96.60   $96.60  
  Purchase #5 $86.51   11.212%   $96.2095   $96.21   $96.20   $96.20  
  Purchase #6 $77.53   9.382%   $84.8039   $84.80   $84.80   $84.80  
  Purchase #7 $218.38   11.175%   $242.784   $242.78   $242.80   $242.80  
  7 purchase totals = $992.39       $1,075.3250   $1,075.32   $1,075.35   $1,075.30