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 $233.50   8.148%   $252.5256   $252.53   $252.55   $252.50  
  Purchase #2 $38.80   7.188%   $41.5889   $41.59   $41.60   $41.60  
  Purchase #3 $164.68   7.272%   $176.6555   $176.66   $176.65   $176.70  
  Purchase #4 $198.29   3.233%   $204.7007   $204.70   $204.70   $204.70  
  Purchase #5 $130.56   12.499%   $146.8787   $146.88   $146.90   $146.90  
  Purchase #6 $55.35   11.719%   $61.8365   $61.84   $61.85   $61.80  
  Purchase #7 $201.28   5.217%   $211.7808   $211.78   $211.80   $211.80  
  7 purchase totals = $1,022.46       $1,095.9667   $1,095.98   $1,096.05   $1,096.00