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 $68.44   7.789%   $73.7708   $73.77   $73.75   $73.80  
  Purchase #2 $217.69   8.367%   $235.9041   $235.90   $235.90   $235.90  
  Purchase #3 $225.70   7.219%   $241.9933   $241.99   $242.00   $242.00  
  Purchase #4 $22.49   4.562%   $23.516   $23.52   $23.50   $23.50  
  Purchase #5 $229.80   12.729%   $259.0512   $259.05   $259.05   $259.10  
  Purchase #6 $149.77   11.435%   $166.8962   $166.90   $166.90   $166.90  
  Purchase #7 $160.54   9.595%   $175.9438   $175.94   $175.95   $175.90  
  7 purchase totals = $1,074.43       $1,177.0754   $1,177.07   $1,177.05   $1,177.10