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 $80.29   7.179%   $86.054   $86.05   $86.05   $86.10  
  Purchase #2 $112.86   9.592%   $123.6855   $123.69   $123.70   $123.70  
  Purchase #3 $211.78   7.845%   $228.3941   $228.39   $228.40   $228.40  
  Purchase #4 $184.77   5.312%   $194.585   $194.59   $194.60   $194.60  
  Purchase #5 $217.54   11.406%   $242.3526   $242.35   $242.35   $242.40  
  Purchase #6 $227.95   11.372%   $253.8725   $253.87   $253.85   $253.90  
  Purchase #7 $92.39   5.816%   $97.7634   $97.76   $97.75   $97.80  
  7 purchase totals = $1,127.58       $1,226.7071   $1,226.70   $1,226.70   $1,226.90