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 $86.68   11.689%   $96.812   $96.81   $96.80   $96.80  
  Purchase #2 $58.85   3.664%   $61.0063   $61.01   $61.00   $61.00  
  Purchase #3 $126.51   3.118%   $130.4546   $130.45   $130.45   $130.50  
  Purchase #4 $236.64   4.377%   $246.9977   $247.00   $247.00   $247.00  
  Purchase #5 $160.55   5.387%   $169.1988   $169.20   $169.20   $169.20  
  Purchase #6 $53.87   4.357%   $56.2171   $56.22   $56.20   $56.20  
  Purchase #7 $216.36   8.412%   $234.5602   $234.56   $234.55   $234.60  
  7 purchase totals = $939.46       $995.2467   $995.25   $995.20   $995.30