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 $183.88   4.772%   $192.6548   $192.65   $192.65   $192.70  
  Purchase #2 $61.98   3.240%   $63.9882   $63.99   $64.00   $64.00  
  Purchase #3 $114.76   11.476%   $127.9299   $127.93   $127.95   $127.90  
  Purchase #4 $109.78   12.339%   $123.3258   $123.33   $123.35   $123.30  
  Purchase #5 $104.95   12.391%   $117.9544   $117.95   $117.95   $118.00  
  Purchase #6 $201.96   11.568%   $225.3227   $225.32   $225.30   $225.30  
  Purchase #7 $200.34   3.247%   $206.845   $206.85   $206.85   $206.80  
  7 purchase totals = $977.65       $1,058.0208   $1,058.02   $1,058.05   $1,058.00