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 $44.62   10.233%   $49.186   $49.19   $49.20   $49.20  
  Purchase #2 $233.49   12.395%   $262.4311   $262.43   $262.45   $262.40  
  Purchase #3 $214.46   10.147%   $236.2213   $236.22   $236.20   $236.20  
  Purchase #4 $24.55   9.448%   $26.8695   $26.87   $26.85   $26.90  
  Purchase #5 $244.27   11.695%   $272.8374   $272.84   $272.85   $272.80  
  Purchase #6 $104.58   4.697%   $109.4921   $109.49   $109.50   $109.50  
  Purchase #7 $115.55   4.298%   $120.5163   $120.52   $120.50   $120.50  
  7 purchase totals = $981.52       $1,077.5537   $1,077.56   $1,077.55   $1,077.50