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 $162.61   8.349%   $176.1863   $176.19   $176.20   $176.20  
  Purchase #2 $133.53   11.322%   $148.6483   $148.65   $148.65   $148.60  
  Purchase #3 $222.34   11.619%   $248.1737   $248.17   $248.15   $248.20  
  Purchase #4 $211.93   8.680%   $230.3255   $230.33   $230.35   $230.30  
  Purchase #5 $31.75   4.417%   $33.1524   $33.15   $33.15   $33.20  
  Purchase #6 $105.60   5.375%   $111.276   $111.28   $111.30   $111.30  
  Purchase #7 $91.31   3.294%   $94.3178   $94.32   $94.30   $94.30  
  7 purchase totals = $959.07       $1,042.0800   $1,042.09   $1,042.10   $1,042.10