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 $52.94   11.557%   $59.0583   $59.06   $59.05   $59.10  
  Purchase #2 $192.55   7.113%   $206.2461   $206.25   $206.25   $206.20  
  Purchase #3 $232.61   9.583%   $254.901   $254.90   $254.90   $254.90  
  Purchase #4 $169.69   8.119%   $183.4671   $183.47   $183.45   $183.50  
  Purchase #5 $62.26   4.791%   $65.2429   $65.24   $65.25   $65.20  
  Purchase #6 $194.82   5.827%   $206.1722   $206.17   $206.15   $206.20  
  Purchase #7 $150.86   5.795%   $159.6023   $159.60   $159.60   $159.60  
  7 purchase totals = $1,055.73       $1,134.6899   $1,134.69   $1,134.65   $1,134.70