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 $69.77   9.241%   $76.2174   $76.22   $76.20   $76.20  
  Purchase #2 $177.83   10.418%   $196.3563   $196.36   $196.35   $196.40  
  Purchase #3 $206.98   8.442%   $224.4533   $224.45   $224.45   $224.50  
  Purchase #4 $82.56   5.625%   $87.204   $87.20   $87.20   $87.20  
  Purchase #5 $154.68   9.752%   $169.7644   $169.76   $169.75   $169.80  
  Purchase #6 $159.94   5.363%   $168.5176   $168.52   $168.50   $168.50  
  Purchase #7 $126.60   8.448%   $137.2952   $137.30   $137.30   $137.30  
  7 purchase totals = $978.36       $1,059.8082   $1,059.81   $1,059.75   $1,059.90