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 $196.33   9.236%   $214.463   $214.46   $214.45   $214.50  
  Purchase #2 $186.70   11.298%   $207.7934   $207.79   $207.80   $207.80  
  Purchase #3 $13.26   9.362%   $14.5014   $14.50   $14.50   $14.50  
  Purchase #4 $159.37   10.769%   $176.5326   $176.53   $176.55   $176.50  
  Purchase #5 $203.63   11.210%   $226.4569   $226.46   $226.45   $226.50  
  Purchase #6 $125.26   3.114%   $129.1606   $129.16   $129.15   $129.20  
  Purchase #7 $139.48   4.170%   $145.2963   $145.30   $145.30   $145.30  
  7 purchase totals = $1,024.03       $1,114.2042   $1,114.20   $1,114.20   $1,114.30