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 $61.52   3.152%   $63.4591   $63.46   $63.45   $63.50  
  Purchase #2 $212.70   13.410%   $241.2231   $241.22   $241.20   $241.20  
  Purchase #3 $232.79   5.860%   $246.4315   $246.43   $246.45   $246.40  
  Purchase #4 $162.66   9.118%   $177.4913   $177.49   $177.50   $177.50  
  Purchase #5 $141.36   10.319%   $155.9469   $155.95   $155.95   $155.90  
  Purchase #6 $210.93   5.278%   $222.0629   $222.06   $222.05   $222.10  
  Purchase #7 $27.49   9.646%   $30.1417   $30.14   $30.15   $30.10  
  7 purchase totals = $1,049.45       $1,136.7565   $1,136.75   $1,136.75   $1,136.70