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 $56.94   9.281%   $62.2246   $62.22   $62.20   $62.20  
  Purchase #2 $183.57   5.455%   $193.5837   $193.58   $193.60   $193.60  
  Purchase #3 $31.83   11.703%   $35.5551   $35.56   $35.55   $35.60  
  Purchase #4 $151.32   7.636%   $162.8748   $162.87   $162.85   $162.90  
  Purchase #5 $110.27   12.752%   $124.3316   $124.33   $124.35   $124.30  
  Purchase #6 $5.95   9.707%   $6.5276   $6.53   $6.55   $6.50  
  Purchase #7 $162.29   4.849%   $170.1594   $170.16   $170.15   $170.20  
  7 purchase totals = $702.17       $755.2568   $755.25   $755.25   $755.30