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 $84.40   12.524%   $94.9703   $94.97   $94.95   $95.00  
  Purchase #2 $136.73   13.632%   $155.369   $155.37   $155.35   $155.40  
  Purchase #3 $131.54   13.396%   $149.1611   $149.16   $149.15   $149.20  
  Purchase #4 $139.74   11.146%   $155.3154   $155.32   $155.30   $155.30  
  Purchase #5 $185.47   6.463%   $197.4569   $197.46   $197.45   $197.50  
  Purchase #6 $70.50   8.585%   $76.5524   $76.55   $76.55   $76.60  
  Purchase #7 $97.34   5.824%   $103.0091   $103.01   $103.00   $103.00  
  7 purchase totals = $845.72       $931.8342   $931.84   $931.75   $932.00