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 $96.99   8.795%   $105.5203   $105.52   $105.50   $105.50  
  Purchase #2 $219.41   5.372%   $231.1967   $231.20   $231.20   $231.20  
  Purchase #3 $176.30   13.219%   $199.6051   $199.61   $199.60   $199.60  
  Purchase #4 $187.71   11.744%   $209.7547   $209.75   $209.75   $209.80  
  Purchase #5 $47.67   11.284%   $53.0491   $53.05   $53.05   $53.00  
  Purchase #6 $136.45   9.561%   $149.496   $149.50   $149.50   $149.50  
  Purchase #7 $192.55   11.468%   $214.6316   $214.63   $214.65   $214.60  
  7 purchase totals = $1,057.08       $1,163.2535   $1,163.26   $1,163.25   $1,163.20