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 $70.86   7.711%   $76.324   $76.32   $76.30   $76.30  
  Purchase #2 $241.89   11.399%   $269.463   $269.46   $269.45   $269.50  
  Purchase #3 $233.83   13.363%   $265.0767   $265.08   $265.10   $265.10  
  Purchase #4 $127.44   13.631%   $144.8113   $144.81   $144.80   $144.80  
  Purchase #5 $133.72   11.406%   $148.9721   $148.97   $148.95   $149.00  
  Purchase #6 $226.75   5.574%   $239.389   $239.39   $239.40   $239.40  
  Purchase #7 $57.74   5.500%   $60.9157   $60.92   $60.90   $60.90  
  7 purchase totals = $1,092.23       $1,204.9518   $1,204.95   $1,204.90   $1,205.00