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 $63.99   12.475%   $71.9728   $71.97   $71.95   $72.00  
  Purchase #2 $44.51   10.121%   $49.0149   $49.01   $49.00   $49.00  
  Purchase #3 $165.46   4.610%   $173.0877   $173.09   $173.10   $173.10  
  Purchase #4 $235.51   10.604%   $260.4835   $260.48   $260.50   $260.50  
  Purchase #5 $239.37   12.614%   $269.5641   $269.56   $269.55   $269.60  
  Purchase #6 $231.52   9.660%   $253.8848   $253.88   $253.90   $253.90  
  Purchase #7 $38.49   6.533%   $41.0046   $41.00   $41.00   $41.00  
  7 purchase totals = $1,018.85       $1,119.0124   $1,118.99   $1,119.00   $1,119.10