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 $44.42   5.503%   $46.8644   $46.86   $46.85   $46.90  
  Purchase #2 $15.49   4.589%   $16.2008   $16.20   $16.20   $16.20  
  Purchase #3 $186.49   3.323%   $192.6871   $192.69   $192.70   $192.70  
  Purchase #4 $166.27   8.727%   $180.7804   $180.78   $180.80   $180.80  
  Purchase #5 $171.93   5.771%   $181.8521   $181.85   $181.85   $181.90  
  Purchase #6 $163.72   5.353%   $172.4839   $172.48   $172.50   $172.50  
  Purchase #7 $9.78   11.719%   $10.9261   $10.93   $10.95   $10.90  
  7 purchase totals = $758.10       $801.7948   $801.79   $801.85   $801.90