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 $55.45   9.182%   $60.5414   $60.54   $60.55   $60.50  
  Purchase #2 $178.89   8.493%   $194.0831   $194.08   $194.10   $194.10  
  Purchase #3 $160.58   8.115%   $173.6111   $173.61   $173.60   $173.60  
  Purchase #4 $68.71   8.158%   $74.3154   $74.32   $74.30   $74.30  
  Purchase #5 $54.91   6.596%   $58.5319   $58.53   $58.55   $58.50  
  Purchase #6 $137.57   11.422%   $153.2832   $153.28   $153.30   $153.30  
  Purchase #7 $20.88   7.634%   $22.474   $22.47   $22.45   $22.50  
  7 purchase totals = $676.99       $736.8401   $736.83   $736.85   $736.80