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 $170.41   8.163%   $184.3206   $184.32   $184.30   $184.30  
  Purchase #2 $162.72   10.192%   $179.3044   $179.30   $179.30   $179.30  
  Purchase #3 $47.40   7.825%   $51.1091   $51.11   $51.10   $51.10  
  Purchase #4 $229.97   5.691%   $243.0576   $243.06   $243.05   $243.10  
  Purchase #5 $54.37   3.396%   $56.2164   $56.22   $56.20   $56.20  
  Purchase #6 $231.46   6.617%   $246.7757   $246.78   $246.80   $246.80  
  Purchase #7 $73.50   3.728%   $76.2401   $76.24   $76.25   $76.20  
  7 purchase totals = $969.83       $1,037.0239   $1,037.03   $1,037.00   $1,037.00