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 $194.71   3.719%   $201.9513   $201.95   $201.95   $202.00  
  Purchase #2 $23.42   6.363%   $24.9102   $24.91   $24.90   $24.90  
  Purchase #3 $77.95   11.190%   $86.6726   $86.67   $86.65   $86.70  
  Purchase #4 $151.33   9.761%   $166.1013   $166.10   $166.10   $166.10  
  Purchase #5 $161.78   13.277%   $183.2595   $183.26   $183.25   $183.30  
  Purchase #6 $188.29   10.389%   $207.8514   $207.85   $207.85   $207.90  
  Purchase #7 $225.25   6.571%   $240.0512   $240.05   $240.05   $240.10  
  7 purchase totals = $1,022.73       $1,110.7975   $1,110.79   $1,110.75   $1,111.00