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 $204.60   10.785%   $226.6661   $226.67   $226.65   $226.70  
  Purchase #2 $62.30   6.392%   $66.2822   $66.28   $66.30   $66.30  
  Purchase #3 $171.26   5.851%   $181.2804   $181.28   $181.30   $181.30  
  Purchase #4 $181.73   8.252%   $196.7264   $196.73   $196.75   $196.70  
  Purchase #5 $58.79   3.108%   $60.6172   $60.62   $60.60   $60.60  
  Purchase #6 $187.77   5.473%   $198.0467   $198.05   $198.05   $198.00  
  Purchase #7 $200.60   12.325%   $225.324   $225.32   $225.30   $225.30  
  7 purchase totals = $1,067.05       $1,154.9430   $1,154.95   $1,154.95   $1,154.90