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 $172.29   13.557%   $195.6474   $195.65   $195.65   $195.60  
  Purchase #2 $114.77   5.747%   $121.3658   $121.37   $121.35   $121.40  
  Purchase #3 $215.29   4.247%   $224.4334   $224.43   $224.45   $224.40  
  Purchase #4 $71.76   3.452%   $74.2372   $74.24   $74.25   $74.20  
  Purchase #5 $212.76   13.646%   $241.7932   $241.79   $241.80   $241.80  
  Purchase #6 $8.37   3.288%   $8.6452   $8.65   $8.65   $8.60  
  Purchase #7 $226.35   3.813%   $234.9807   $234.98   $235.00   $235.00  
  7 purchase totals = $1,021.59       $1,101.1029   $1,101.11   $1,101.15   $1,101.00