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 $67.72   5.640%   $71.5394   $71.54   $71.55   $71.50  
  Purchase #2 $179.56   9.153%   $195.9951   $196.00   $196.00   $196.00  
  Purchase #3 $118.94   5.222%   $125.151   $125.15   $125.15   $125.20  
  Purchase #4 $147.31   5.509%   $155.4253   $155.43   $155.45   $155.40  
  Purchase #5 $183.73   7.522%   $197.5502   $197.55   $197.55   $197.60  
  Purchase #6 $232.47   3.154%   $239.8021   $239.80   $239.80   $239.80  
  Purchase #7 $197.63   8.530%   $214.4878   $214.49   $214.50   $214.50  
  7 purchase totals = $1,127.36       $1,199.9509   $1,199.96   $1,200.00   $1,200.00