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 $85.93   11.241%   $95.5894   $95.59   $95.60   $95.60  
  Purchase #2 $248.27   9.779%   $272.5483   $272.55   $272.55   $272.50  
  Purchase #3 $220.92   9.732%   $242.4199   $242.42   $242.40   $242.40  
  Purchase #4 $220.65   8.580%   $239.5818   $239.58   $239.60   $239.60  
  Purchase #5 $245.60   4.620%   $256.9467   $256.95   $256.95   $256.90  
  Purchase #6 $240.89   4.631%   $252.0456   $252.05   $252.05   $252.00  
  Purchase #7 $7.35   8.453%   $7.9713   $7.97   $7.95   $8.00  
  7 purchase totals = $1,269.61       $1,367.1030   $1,367.11   $1,367.10   $1,367.00