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 $147.53   9.608%   $161.7047   $161.70   $161.70   $161.70  
  Purchase #2 $51.72   7.129%   $55.4071   $55.41   $55.40   $55.40  
  Purchase #3 $195.49   12.424%   $219.7777   $219.78   $219.80   $219.80  
  Purchase #4 $172.68   12.304%   $193.9265   $193.93   $193.95   $193.90  
  Purchase #5 $239.69   4.578%   $250.663   $250.66   $250.65   $250.70  
  Purchase #6 $5.91   5.388%   $6.2284   $6.23   $6.25   $6.20  
  Purchase #7 $64.49   4.664%   $67.4978   $67.50   $67.50   $67.50  
  7 purchase totals = $877.51       $955.2052   $955.21   $955.25   $955.20