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 $208.49   11.413%   $232.285   $232.29   $232.30   $232.30  
  Purchase #2 $33.88   4.154%   $35.2874   $35.29   $35.30   $35.30  
  Purchase #3 $183.32   9.250%   $200.2771   $200.28   $200.30   $200.30  
  Purchase #4 $67.66   12.835%   $76.3442   $76.34   $76.35   $76.30  
  Purchase #5 $84.51   11.249%   $94.0165   $94.02   $94.00   $94.00  
  Purchase #6 $245.51   9.527%   $268.8997   $268.90   $268.90   $268.90  
  Purchase #7 $107.99   9.861%   $118.6389   $118.64   $118.65   $118.60  
  7 purchase totals = $931.36       $1,025.7488   $1,025.76   $1,025.80   $1,025.70