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 $32.37   11.146%   $35.978   $35.98   $36.00   $36.00  
  Purchase #2 $103.85   13.847%   $118.2301   $118.23   $118.25   $118.20  
  Purchase #3 $45.41   4.367%   $47.3931   $47.39   $47.40   $47.40  
  Purchase #4 $219.97   5.105%   $231.1995   $231.20   $231.20   $231.20  
  Purchase #5 $39.80   3.169%   $41.0613   $41.06   $41.05   $41.10  
  Purchase #6 $233.79   4.438%   $244.1656   $244.17   $244.15   $244.20  
  Purchase #7 $176.33   12.700%   $198.7239   $198.72   $198.70   $198.70  
  7 purchase totals = $851.52       $916.7515   $916.75   $916.75   $916.80