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 $160.30   10.267%   $176.758   $176.76   $176.75   $176.80  
  Purchase #2 $230.40   7.237%   $247.074   $247.07   $247.05   $247.10  
  Purchase #3 $205.62   4.286%   $214.4329   $214.43   $214.45   $214.40  
  Purchase #4 $184.92   7.380%   $198.5671   $198.57   $198.55   $198.60  
  Purchase #5 $73.87   11.169%   $82.1205   $82.12   $82.10   $82.10  
  Purchase #6 $242.73   13.825%   $276.2874   $276.29   $276.30   $276.30  
  Purchase #7 $243.53   3.678%   $252.487   $252.49   $252.50   $252.50  
  7 purchase totals = $1,341.37       $1,447.7269   $1,447.73   $1,447.70   $1,447.80