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 $162.87   8.411%   $176.569   $176.57   $176.55   $176.60  
  Purchase #2 $231.57   13.228%   $262.2021   $262.20   $262.20   $262.20  
  Purchase #3 $168.54   12.209%   $189.117   $189.12   $189.10   $189.10  
  Purchase #4 $107.63   8.252%   $116.5116   $116.51   $116.50   $116.50  
  Purchase #5 $49.95   10.852%   $55.3706   $55.37   $55.35   $55.40  
  Purchase #6 $63.91   4.642%   $66.8767   $66.88   $66.90   $66.90  
  Purchase #7 $138.95   8.527%   $150.7983   $150.80   $150.80   $150.80  
  7 purchase totals = $923.42       $1,017.4453   $1,017.45   $1,017.40   $1,017.50