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 $85.28   13.318%   $96.6376   $96.64   $96.65   $96.60  
  Purchase #2 $232.31   11.558%   $259.1604   $259.16   $259.15   $259.20  
  Purchase #3 $118.55   3.492%   $122.6898   $122.69   $122.70   $122.70  
  Purchase #4 $99.30   8.257%   $107.4992   $107.50   $107.50   $107.50  
  Purchase #5 $59.33   4.450%   $61.9702   $61.97   $61.95   $62.00  
  Purchase #6 $89.25   4.325%   $93.1101   $93.11   $93.10   $93.10  
  Purchase #7 $211.93   4.705%   $221.9013   $221.90   $221.90   $221.90  
  7 purchase totals = $895.95       $962.9686   $962.97   $962.95   $963.00