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 $64.34   8.408%   $69.7497   $69.75   $69.75   $69.70  
  Purchase #2 $236.61   13.703%   $269.0327   $269.03   $269.05   $269.00  
  Purchase #3 $61.91   10.691%   $68.5288   $68.53   $68.55   $68.50  
  Purchase #4 $226.70   8.199%   $245.2871   $245.29   $245.30   $245.30  
  Purchase #5 $103.94   12.241%   $116.6633   $116.66   $116.65   $116.70  
  Purchase #6 $190.25   7.179%   $203.908   $203.91   $203.90   $203.90  
  Purchase #7 $35.29   4.823%   $36.992   $36.99   $37.00   $37.00  
  7 purchase totals = $919.04       $1,010.1616   $1,010.16   $1,010.20   $1,010.10