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 $84.34   12.645%   $95.0048   $95.00   $95.00   $95.00  
  Purchase #2 $91.91   5.644%   $97.0974   $97.10   $97.10   $97.10  
  Purchase #3 $36.58   9.593%   $40.0891   $40.09   $40.10   $40.10  
  Purchase #4 $164.96   10.672%   $182.5645   $182.56   $182.55   $182.60  
  Purchase #5 $24.80   4.810%   $25.9929   $25.99   $26.00   $26.00  
  Purchase #6 $19.61   11.855%   $21.9348   $21.93   $21.95   $21.90  
  Purchase #7 $181.68   5.827%   $192.2665   $192.27   $192.25   $192.30  
  7 purchase totals = $603.88       $654.9500   $654.94   $654.95   $655.00