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 $187.45   6.795%   $200.1872   $200.19   $200.20   $200.20  
  Purchase #2 $136.82   12.827%   $154.3699   $154.37   $154.35   $154.40  
  Purchase #3 $127.98   12.827%   $144.396   $144.40   $144.40   $144.40  
  Purchase #4 $212.61   3.325%   $219.6793   $219.68   $219.70   $219.70  
  Purchase #5 $199.91   3.501%   $206.9088   $206.91   $206.90   $206.90  
  Purchase #6 $141.58   10.195%   $156.0141   $156.01   $156.00   $156.00  
  Purchase #7 $43.46   6.732%   $46.3857   $46.39   $46.40   $46.40  
  7 purchase totals = $1,049.81       $1,127.9410   $1,127.95   $1,127.95   $1,128.00