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 $61.55   12.545%   $69.2714   $69.27   $69.25   $69.30  
  Purchase #2 $200.36   9.538%   $219.4703   $219.47   $219.45   $219.50  
  Purchase #3 $91.76   10.111%   $101.0379   $101.04   $101.05   $101.00  
  Purchase #4 $35.41   8.504%   $38.4213   $38.42   $38.40   $38.40  
  Purchase #5 $249.52   4.218%   $260.0448   $260.04   $260.05   $260.00  
  Purchase #6 $237.91   13.300%   $269.552   $269.55   $269.55   $269.60  
  Purchase #7 $214.89   13.365%   $243.61   $243.61   $243.60   $243.60  
  7 purchase totals = $1,091.40       $1,201.4077   $1,201.40   $1,201.35   $1,201.40