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 $61.82   11.548%   $68.959   $68.96   $68.95   $69.00  
  Purchase #2 $214.39   3.731%   $222.3889   $222.39   $222.40   $222.40  
  Purchase #3 $183.53   9.310%   $200.6166   $200.62   $200.60   $200.60  
  Purchase #4 $103.66   13.585%   $117.7422   $117.74   $117.75   $117.70  
  Purchase #5 $206.48   6.154%   $219.1868   $219.19   $219.20   $219.20  
  Purchase #6 $205.59   4.528%   $214.8991   $214.90   $214.90   $214.90  
  Purchase #7 $171.77   13.792%   $195.4605   $195.46   $195.45   $195.50  
  7 purchase totals = $1,147.24       $1,239.2531   $1,239.26   $1,239.25   $1,239.30