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 $32.56   4.490%   $34.0219   $34.02   $34.00   $34.00  
  Purchase #2 $203.33   8.742%   $221.1051   $221.11   $221.10   $221.10  
  Purchase #3 $215.66   8.874%   $234.7977   $234.80   $234.80   $234.80  
  Purchase #4 $81.51   11.666%   $91.019   $91.02   $91.00   $91.00  
  Purchase #5 $195.60   9.749%   $214.669   $214.67   $214.65   $214.70  
  Purchase #6 $163.73   13.585%   $185.9727   $185.97   $185.95   $186.00  
  Purchase #7 $143.44   13.480%   $162.7757   $162.78   $162.80   $162.80  
  7 purchase totals = $1,035.83       $1,144.3611   $1,144.37   $1,144.30   $1,144.40