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 $195.26   9.726%   $214.251   $214.25   $214.25   $214.30  
  Purchase #2 $42.89   7.545%   $46.1261   $46.13   $46.15   $46.10  
  Purchase #3 $103.68   10.334%   $114.3943   $114.39   $114.40   $114.40  
  Purchase #4 $195.29   9.120%   $213.1004   $213.10   $213.10   $213.10  
  Purchase #5 $198.77   13.162%   $224.9321   $224.93   $224.95   $224.90  
  Purchase #6 $147.46   3.755%   $152.9971   $153.00   $153.00   $153.00  
  Purchase #7 $74.28   13.400%   $84.2335   $84.23   $84.25   $84.20  
  7 purchase totals = $957.63       $1,050.0345   $1,050.03   $1,050.10   $1,050.00