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 $216.78   4.624%   $226.8039   $226.80   $226.80   $226.80  
  Purchase #2 $205.32   13.643%   $233.3318   $233.33   $233.35   $233.30  
  Purchase #3 $121.78   8.214%   $131.783   $131.78   $131.80   $131.80  
  Purchase #4 $43.44   4.423%   $45.3614   $45.36   $45.35   $45.40  
  Purchase #5 $249.64   6.496%   $265.8566   $265.86   $265.85   $265.90  
  Purchase #6 $245.56   8.400%   $266.187   $266.19   $266.20   $266.20  
  Purchase #7 $226.91   6.233%   $241.0533   $241.05   $241.05   $241.10  
  7 purchase totals = $1,309.43       $1,410.3770   $1,410.37   $1,410.40   $1,410.50