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 $223.34   9.675%   $244.9481   $244.95   $244.95   $244.90  
  Purchase #2 $28.60   6.123%   $30.3512   $30.35   $30.35   $30.40  
  Purchase #3 $167.92   12.846%   $189.491   $189.49   $189.50   $189.50  
  Purchase #4 $15.28   13.232%   $17.3018   $17.30   $17.30   $17.30  
  Purchase #5 $190.84   12.114%   $213.9584   $213.96   $213.95   $214.00  
  Purchase #6 $60.31   10.298%   $66.5207   $66.52   $66.50   $66.50  
  Purchase #7 $217.25   6.660%   $231.7189   $231.72   $231.70   $231.70  
  7 purchase totals = $903.54       $994.2901   $994.29   $994.25   $994.30