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 $216.94   11.387%   $241.643   $241.64   $241.65   $241.60  
  Purchase #2 $200.44   3.602%   $207.6598   $207.66   $207.65   $207.70  
  Purchase #3 $90.79   4.470%   $94.8483   $94.85   $94.85   $94.80  
  Purchase #4 $145.44   12.313%   $163.348   $163.35   $163.35   $163.30  
  Purchase #5 $240.68   11.864%   $269.2343   $269.23   $269.25   $269.20  
  Purchase #6 $52.34   10.789%   $57.987   $57.99   $58.00   $58.00  
  Purchase #7 $171.28   13.556%   $194.4987   $194.50   $194.50   $194.50  
  7 purchase totals = $1,117.91       $1,229.2191   $1,229.22   $1,229.25   $1,229.10