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 $211.95   9.479%   $232.0407   $232.04   $232.05   $232.00  
  Purchase #2 $62.69   6.162%   $66.553   $66.55   $66.55   $66.60  
  Purchase #3 $74.59   8.620%   $81.0197   $81.02   $81.00   $81.00  
  Purchase #4 $59.88   6.353%   $63.6842   $63.68   $63.70   $63.70  
  Purchase #5 $33.46   13.224%   $37.8848   $37.88   $37.90   $37.90  
  Purchase #6 $80.70   12.232%   $90.5712   $90.57   $90.55   $90.60  
  Purchase #7 $150.27   6.647%   $160.2584   $160.26   $160.25   $160.30  
  7 purchase totals = $673.54       $732.0120   $732.00   $732.00   $732.10