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 $215.55   3.468%   $223.0253   $223.03   $223.05   $223.00  
  Purchase #2 $234.43   13.325%   $265.6678   $265.67   $265.65   $265.70  
  Purchase #3 $61.34   9.711%   $67.2967   $67.30   $67.30   $67.30  
  Purchase #4 $201.95   3.155%   $208.3215   $208.32   $208.30   $208.30  
  Purchase #5 $64.28   4.546%   $67.2022   $67.20   $67.20   $67.20  
  Purchase #6 $161.71   13.207%   $183.067   $183.07   $183.05   $183.10  
  Purchase #7 $128.93   4.242%   $134.3992   $134.40   $134.40   $134.40  
  7 purchase totals = $1,068.19       $1,148.9797   $1,148.99   $1,148.95   $1,149.00