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 $181.84   7.440%   $195.3689   $195.37   $195.35   $195.40  
  Purchase #2 $161.77   13.297%   $183.2806   $183.28   $183.30   $183.30  
  Purchase #3 $39.73   11.849%   $44.4376   $44.44   $44.45   $44.40  
  Purchase #4 $224.74   11.285%   $250.1019   $250.10   $250.10   $250.10  
  Purchase #5 $92.34   5.364%   $97.2931   $97.29   $97.30   $97.30  
  Purchase #6 $86.51   5.508%   $91.275   $91.28   $91.30   $91.30  
  Purchase #7 $193.84   10.613%   $214.4122   $214.41   $214.40   $214.40  
  7 purchase totals = $980.77       $1,076.1693   $1,076.17   $1,076.20   $1,076.20