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 $41.47   5.409%   $43.7131   $43.71   $43.70   $43.70  
  Purchase #2 $214.59   9.427%   $234.8194   $234.82   $234.80   $234.80  
  Purchase #3 $244.85   8.620%   $265.9561   $265.96   $265.95   $266.00  
  Purchase #4 $158.52   9.450%   $173.5001   $173.50   $173.50   $173.50  
  Purchase #5 $10.40   11.750%   $11.622   $11.62   $11.60   $11.60  
  Purchase #6 $34.68   9.553%   $37.993   $37.99   $38.00   $38.00  
  Purchase #7 $87.42   5.801%   $92.4912   $92.49   $92.50   $92.50  
  7 purchase totals = $791.93       $860.0949   $860.09   $860.05   $860.10