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 $32.48   5.309%   $34.2044   $34.20   $34.20   $34.20  
  Purchase #2 $186.46   7.201%   $199.887   $199.89   $199.90   $199.90  
  Purchase #3 $225.66   10.598%   $249.5754   $249.58   $249.60   $249.60  
  Purchase #4 $64.28   10.417%   $70.976   $70.98   $71.00   $71.00  
  Purchase #5 $71.58   4.402%   $74.731   $74.73   $74.75   $74.70  
  Purchase #6 $236.75   13.823%   $269.476   $269.48   $269.50   $269.50  
  Purchase #7 $121.54   3.734%   $126.0783   $126.08   $126.10   $126.10  
  7 purchase totals = $938.75       $1,024.9281   $1,024.94   $1,025.05   $1,025.00