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 $176.86   13.252%   $200.2975   $200.30   $200.30   $200.30  
  Purchase #2 $44.35   10.273%   $48.9061   $48.91   $48.90   $48.90  
  Purchase #3 $167.68   8.187%   $181.408   $181.41   $181.40   $181.40  
  Purchase #4 $232.97   3.167%   $240.3482   $240.35   $240.35   $240.30  
  Purchase #5 $99.63   5.785%   $105.3936   $105.39   $105.40   $105.40  
  Purchase #6 $63.91   3.680%   $66.2619   $66.26   $66.25   $66.30  
  Purchase #7 $182.25   13.801%   $207.4023   $207.40   $207.40   $207.40  
  7 purchase totals = $967.65       $1,050.0176   $1,050.02   $1,050.00   $1,050.00