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 $67.58   9.724%   $74.1515   $74.15   $74.15   $74.20  
  Purchase #2 $226.40   4.840%   $237.3578   $237.36   $237.35   $237.40  
  Purchase #3 $101.78   12.468%   $114.4699   $114.47   $114.45   $114.50  
  Purchase #4 $31.77   4.335%   $33.1472   $33.15   $33.15   $33.10  
  Purchase #5 $163.73   8.618%   $177.8403   $177.84   $177.85   $177.80  
  Purchase #6 $213.86   13.761%   $243.2893   $243.29   $243.30   $243.30  
  Purchase #7 $69.33   6.345%   $73.729   $73.73   $73.75   $73.70  
  7 purchase totals = $874.45       $953.9850   $953.99   $954.00   $954.00