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 $43.29   11.307%   $48.1848   $48.18   $48.20   $48.20  
  Purchase #2 $206.56   3.407%   $213.5975   $213.60   $213.60   $213.60  
  Purchase #3 $33.62   5.132%   $35.3454   $35.35   $35.35   $35.30  
  Purchase #4 $103.77   10.286%   $114.4438   $114.44   $114.45   $114.40  
  Purchase #5 $208.52   12.572%   $234.7351   $234.74   $234.75   $234.70  
  Purchase #6 $156.42   6.562%   $166.6843   $166.68   $166.70   $166.70  
  Purchase #7 $181.63   6.859%   $194.088   $194.09   $194.10   $194.10  
  7 purchase totals = $933.81       $1,007.0789   $1,007.08   $1,007.15   $1,007.00