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 $86.68   9.177%   $94.6346   $94.63   $94.65   $94.60  
  Purchase #2 $182.44   13.453%   $206.9837   $206.98   $207.00   $207.00  
  Purchase #3 $173.78   11.399%   $193.5892   $193.59   $193.60   $193.60  
  Purchase #4 $222.98   7.741%   $240.2409   $240.24   $240.25   $240.20  
  Purchase #5 $143.30   7.674%   $154.2968   $154.30   $154.30   $154.30  
  Purchase #6 $41.52   4.153%   $43.2443   $43.24   $43.25   $43.20  
  Purchase #7 $110.34   10.389%   $121.8032   $121.80   $121.80   $121.80  
  7 purchase totals = $961.04       $1,054.7927   $1,054.78   $1,054.85   $1,054.70