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 $64.64   12.388%   $72.6476   $72.65   $72.65   $72.60  
  Purchase #2 $231.76   7.643%   $249.4734   $249.47   $249.45   $249.50  
  Purchase #3 $60.52   10.804%   $67.0586   $67.06   $67.05   $67.10  
  Purchase #4 $199.57   6.399%   $212.3405   $212.34   $212.35   $212.30  
  Purchase #5 $65.60   13.339%   $74.3504   $74.35   $74.35   $74.40  
  Purchase #6 $239.58   5.827%   $253.5403   $253.54   $253.55   $253.50  
  Purchase #7 $29.97   8.662%   $32.566   $32.57   $32.55   $32.60  
  7 purchase totals = $891.64       $961.9768   $961.98   $961.95   $962.00