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 $203.82   5.396%   $214.8181   $214.82   $214.80   $214.80  
  Purchase #2 $27.31   11.794%   $30.5309   $30.53   $30.55   $30.50  
  Purchase #3 $36.25   5.159%   $38.1201   $38.12   $38.10   $38.10  
  Purchase #4 $182.42   5.700%   $192.8179   $192.82   $192.80   $192.80  
  Purchase #5 $108.96   4.421%   $113.7771   $113.78   $113.80   $113.80  
  Purchase #6 $174.88   6.471%   $186.1965   $186.20   $186.20   $186.20  
  Purchase #7 $221.50   5.757%   $234.2518   $234.25   $234.25   $234.30  
  7 purchase totals = $955.14       $1,010.5124   $1,010.52   $1,010.50   $1,010.50