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 $58.71   3.808%   $60.9457   $60.95   $60.95   $60.90  
  Purchase #2 $212.76   5.757%   $225.0086   $225.01   $225.00   $225.00  
  Purchase #3 $219.72   3.528%   $227.4717   $227.47   $227.45   $227.50  
  Purchase #4 $44.59   8.832%   $48.5282   $48.53   $48.55   $48.50  
  Purchase #5 $233.68   5.250%   $245.9482   $245.95   $245.95   $245.90  
  Purchase #6 $99.66   13.294%   $112.9088   $112.91   $112.90   $112.90  
  Purchase #7 $117.44   6.182%   $124.7001   $124.70   $124.70   $124.70  
  7 purchase totals = $986.56       $1,045.5113   $1,045.52   $1,045.50   $1,045.40