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 $103.40   10.273%   $114.0223   $114.02   $114.00   $114.00  
  Purchase #2 $56.50   11.864%   $63.2032   $63.20   $63.20   $63.20  
  Purchase #3 $30.47   4.301%   $31.7805   $31.78   $31.80   $31.80  
  Purchase #4 $210.61   12.819%   $237.6081   $237.61   $237.60   $237.60  
  Purchase #5 $204.79   9.168%   $223.5651   $223.57   $223.55   $223.60  
  Purchase #6 $220.56   13.395%   $250.104   $250.10   $250.10   $250.10  
  Purchase #7 $69.25   9.716%   $75.9783   $75.98   $76.00   $76.00  
  7 purchase totals = $895.58       $996.2615   $996.26   $996.25   $996.30