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 $142.36   6.750%   $151.9693   $151.97   $151.95   $152.00  
  Purchase #2 $163.99   8.364%   $177.7061   $177.71   $177.70   $177.70  
  Purchase #3 $52.25   12.754%   $58.914   $58.91   $58.90   $58.90  
  Purchase #4 $191.66   7.383%   $205.8103   $205.81   $205.80   $205.80  
  Purchase #5 $166.32   10.268%   $183.3977   $183.40   $183.40   $183.40  
  Purchase #6 $176.38   10.287%   $194.5242   $194.52   $194.50   $194.50  
  Purchase #7 $38.69   7.778%   $41.6993   $41.70   $41.70   $41.70  
  7 purchase totals = $931.65       $1,014.0209   $1,014.02   $1,013.95   $1,014.00