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 $191.77   4.858%   $201.0862   $201.09   $201.10   $201.10  
  Purchase #2 $110.34   7.460%   $118.5714   $118.57   $118.55   $118.60  
  Purchase #3 $67.65   3.545%   $70.0482   $70.05   $70.05   $70.00  
  Purchase #4 $166.36   10.176%   $183.2888   $183.29   $183.30   $183.30  
  Purchase #5 $138.73   13.547%   $157.5238   $157.52   $157.50   $157.50  
  Purchase #6 $158.57   6.411%   $168.7359   $168.74   $168.75   $168.70  
  Purchase #7 $234.40   12.230%   $263.0671   $263.07   $263.05   $263.10  
  7 purchase totals = $1,067.82       $1,162.3214   $1,162.33   $1,162.30   $1,162.30