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 $192.27   11.629%   $214.6291   $214.63   $214.65   $214.60  
  Purchase #2 $114.56   9.221%   $125.1236   $125.12   $125.10   $125.10  
  Purchase #3 $204.53   8.254%   $221.4119   $221.41   $221.40   $221.40  
  Purchase #4 $212.29   9.630%   $232.7335   $232.73   $232.75   $232.70  
  Purchase #5 $87.93   8.577%   $95.4718   $95.47   $95.45   $95.50  
  Purchase #6 $100.27   4.655%   $104.9376   $104.94   $104.95   $104.90  
  Purchase #7 $232.26   3.116%   $239.4972   $239.50   $239.50   $239.50  
  7 purchase totals = $1,144.11       $1,233.8047   $1,233.80   $1,233.80   $1,233.70