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 $224.73   10.578%   $248.5019   $248.50   $248.50   $248.50  
  Purchase #2 $43.98   4.872%   $46.1227   $46.12   $46.10   $46.10  
  Purchase #3 $70.66   4.488%   $73.8312   $73.83   $73.85   $73.80  
  Purchase #4 $169.94   3.240%   $175.4461   $175.45   $175.45   $175.40  
  Purchase #5 $239.62   9.457%   $262.2809   $262.28   $262.30   $262.30  
  Purchase #6 $131.35   11.156%   $146.0034   $146.00   $146.00   $146.00  
  Purchase #7 $130.75   9.704%   $143.438   $143.44   $143.45   $143.40  
  7 purchase totals = $1,011.03       $1,095.6242   $1,095.62   $1,095.65   $1,095.50