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 $93.82   3.738%   $97.327   $97.33   $97.35   $97.30  
  Purchase #2 $180.63   8.462%   $195.9149   $195.91   $195.90   $195.90  
  Purchase #3 $21.40   11.691%   $23.9019   $23.90   $23.90   $23.90  
  Purchase #4 $28.94   5.383%   $30.4978   $30.50   $30.50   $30.50  
  Purchase #5 $93.66   3.386%   $96.8313   $96.83   $96.85   $96.80  
  Purchase #6 $8.56   3.516%   $8.861   $8.86   $8.85   $8.90  
  Purchase #7 $228.96   4.239%   $238.6656   $238.67   $238.65   $238.70  
  7 purchase totals = $655.97       $691.9995   $692.00   $692.00   $692.00