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 $86.25   9.754%   $94.6628   $94.66   $94.65   $94.70  
  Purchase #2 $214.74   10.229%   $236.7058   $236.71   $236.70   $236.70  
  Purchase #3 $116.73   4.657%   $122.1661   $122.17   $122.15   $122.20  
  Purchase #4 $246.68   6.441%   $262.5687   $262.57   $262.55   $262.60  
  Purchase #5 $92.28   7.106%   $98.8374   $98.84   $98.85   $98.80  
  Purchase #6 $94.41   8.255%   $102.2035   $102.20   $102.20   $102.20  
  Purchase #7 $114.65   4.840%   $120.1991   $120.20   $120.20   $120.20  
  7 purchase totals = $965.74       $1,037.3434   $1,037.35   $1,037.30   $1,037.40