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 $41.35   5.571%   $43.6536   $43.65   $43.65   $43.70  
  Purchase #2 $174.62   10.743%   $193.3794   $193.38   $193.40   $193.40  
  Purchase #3 $137.63   11.435%   $153.368   $153.37   $153.35   $153.40  
  Purchase #4 $199.68   7.177%   $214.011   $214.01   $214.00   $214.00  
  Purchase #5 $193.56   10.447%   $213.7812   $213.78   $213.80   $213.80  
  Purchase #6 $139.63   8.612%   $151.6549   $151.65   $151.65   $151.70  
  Purchase #7 $172.36   3.145%   $177.7807   $177.78   $177.80   $177.80  
  7 purchase totals = $1,058.83       $1,147.6288   $1,147.62   $1,147.65   $1,147.80