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 $62.75   6.596%   $66.889   $66.89   $66.90   $66.90  
  Purchase #2 $221.43   3.806%   $229.8576   $229.86   $229.85   $229.90  
  Purchase #3 $70.72   3.159%   $72.954   $72.95   $72.95   $73.00  
  Purchase #4 $129.84   11.759%   $145.1079   $145.11   $145.10   $145.10  
  Purchase #5 $164.85   10.651%   $182.4082   $182.41   $182.40   $182.40  
  Purchase #6 $28.29   3.240%   $29.2066   $29.21   $29.20   $29.20  
  Purchase #7 $246.64   5.154%   $259.3518   $259.35   $259.35   $259.40  
  7 purchase totals = $924.52       $985.7751   $985.78   $985.75   $985.90