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 $209.51   6.318%   $222.7468   $222.75   $222.75   $222.70  
  Purchase #2 $90.37   5.118%   $94.9951   $95.00   $95.00   $95.00  
  Purchase #3 $7.91   5.828%   $8.371   $8.37   $8.35   $8.40  
  Purchase #4 $92.35   11.187%   $102.6812   $102.68   $102.70   $102.70  
  Purchase #5 $93.32   8.592%   $101.3381   $101.34   $101.35   $101.30  
  Purchase #6 $248.98   13.463%   $282.5002   $282.50   $282.50   $282.50  
  Purchase #7 $118.69   3.406%   $122.7326   $122.73   $122.75   $122.70  
  7 purchase totals = $861.13       $935.3650   $935.37   $935.40   $935.30