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 $116.74   7.715%   $125.7465   $125.75   $125.75   $125.70  
  Purchase #2 $218.25   9.150%   $238.2199   $238.22   $238.20   $238.20  
  Purchase #3 $118.69   3.429%   $122.7599   $122.76   $122.75   $122.80  
  Purchase #4 $135.65   8.767%   $147.5424   $147.54   $147.55   $147.50  
  Purchase #5 $156.55   11.839%   $175.084   $175.08   $175.10   $175.10  
  Purchase #6 $50.70   7.222%   $54.3616   $54.36   $54.35   $54.40  
  Purchase #7 $87.49   10.866%   $96.9967   $97.00   $97.00   $97.00  
  7 purchase totals = $884.07       $960.7110   $960.71   $960.70   $960.70