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 $141.26   7.706%   $152.1455   $152.15   $152.15   $152.10  
  Purchase #2 $8.77   12.394%   $9.857   $9.86   $9.85   $9.90  
  Purchase #3 $14.85   8.513%   $16.1142   $16.11   $16.10   $16.10  
  Purchase #4 $72.99   6.151%   $77.4796   $77.48   $77.50   $77.50  
  Purchase #5 $127.69   11.145%   $141.9211   $141.92   $141.90   $141.90  
  Purchase #6 $222.95   3.242%   $230.178   $230.18   $230.20   $230.20  
  Purchase #7 $226.55   9.447%   $247.9522   $247.95   $247.95   $248.00  
  7 purchase totals = $815.06       $875.6476   $875.65   $875.65   $875.70