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 $60.79   3.204%   $62.7377   $62.74   $62.75   $62.70  
  Purchase #2 $224.82   9.713%   $246.6568   $246.66   $246.65   $246.70  
  Purchase #3 $227.97   3.553%   $236.0698   $236.07   $236.05   $236.10  
  Purchase #4 $160.80   7.763%   $173.2829   $173.28   $173.30   $173.30  
  Purchase #5 $183.63   3.493%   $190.0442   $190.04   $190.05   $190.00  
  Purchase #6 $160.37   6.356%   $170.5631   $170.56   $170.55   $170.60  
  Purchase #7 $109.94   4.155%   $114.508   $114.51   $114.50   $114.50  
  7 purchase totals = $1,128.32       $1,193.8625   $1,193.86   $1,193.85   $1,193.90