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 $208.58   8.793%   $226.9204   $226.92   $226.90   $226.90  
  Purchase #2 $45.57   5.358%   $48.0116   $48.01   $48.00   $48.00  
  Purchase #3 $217.92   7.754%   $234.8175   $234.82   $234.80   $234.80  
  Purchase #4 $179.57   4.314%   $187.3166   $187.32   $187.30   $187.30  
  Purchase #5 $137.92   6.277%   $146.5772   $146.58   $146.60   $146.60  
  Purchase #6 $47.39   12.764%   $53.4389   $53.44   $53.45   $53.40  
  Purchase #7 $192.28   9.809%   $211.1407   $211.14   $211.15   $211.10  
  7 purchase totals = $1,029.23       $1,108.2229   $1,108.23   $1,108.20   $1,108.10