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 $35.46   4.195%   $36.9475   $36.95   $36.95   $36.90  
  Purchase #2 $244.65   13.225%   $277.005   $277.01   $277.00   $277.00  
  Purchase #3 $234.88   8.418%   $254.6522   $254.65   $254.65   $254.70  
  Purchase #4 $10.62   4.401%   $11.0874   $11.09   $11.10   $11.10  
  Purchase #5 $227.37   4.724%   $238.111   $238.11   $238.10   $238.10  
  Purchase #6 $23.81   10.490%   $26.3077   $26.31   $26.30   $26.30  
  Purchase #7 $217.62   9.309%   $237.8782   $237.88   $237.90   $237.90  
  7 purchase totals = $994.41       $1,081.9890   $1,082.00   $1,082.00   $1,082.00