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 $183.51   10.541%   $202.8538   $202.85   $202.85   $202.90  
  Purchase #2 $155.87   7.121%   $166.9695   $166.97   $166.95   $167.00  
  Purchase #3 $182.83   13.274%   $207.0989   $207.10   $207.10   $207.10  
  Purchase #4 $70.52   4.860%   $73.9473   $73.95   $73.95   $73.90  
  Purchase #5 $107.60   4.105%   $112.017   $112.02   $112.00   $112.00  
  Purchase #6 $186.65   4.426%   $194.9111   $194.91   $194.90   $194.90  
  Purchase #7 $172.83   9.158%   $188.6578   $188.66   $188.65   $188.70  
  7 purchase totals = $1,059.81       $1,146.4554   $1,146.46   $1,146.40   $1,146.50