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 $88.63   9.113%   $96.7069   $96.71   $96.70   $96.70  
  Purchase #2 $166.26   10.367%   $183.4962   $183.50   $183.50   $183.50  
  Purchase #3 $30.34   9.103%   $33.1019   $33.10   $33.10   $33.10  
  Purchase #4 $249.93   5.319%   $263.2238   $263.22   $263.20   $263.20  
  Purchase #5 $218.96   8.584%   $237.7555   $237.76   $237.75   $237.80  
  Purchase #6 $87.25   10.848%   $96.7149   $96.71   $96.70   $96.70  
  Purchase #7 $209.90   3.186%   $216.5874   $216.59   $216.60   $216.60  
  7 purchase totals = $1,051.27       $1,127.5866   $1,127.59   $1,127.55   $1,127.60