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 $59.37   10.533%   $65.6234   $65.62   $65.60   $65.60  
  Purchase #2 $230.41   5.747%   $243.6517   $243.65   $243.65   $243.70  
  Purchase #3 $104.76   6.601%   $111.6752   $111.68   $111.70   $111.70  
  Purchase #4 $162.66   3.341%   $168.0945   $168.09   $168.10   $168.10  
  Purchase #5 $206.92   4.227%   $215.6665   $215.67   $215.65   $215.70  
  Purchase #6 $141.35   7.381%   $151.783   $151.78   $151.80   $151.80  
  Purchase #7 $201.65   8.768%   $219.3307   $219.33   $219.35   $219.30  
  7 purchase totals = $1,107.12       $1,175.8250   $1,175.82   $1,175.85   $1,175.90