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 $48.96   9.813%   $53.7644   $53.76   $53.75   $53.80  
  Purchase #2 $228.91   4.529%   $239.2773   $239.28   $239.30   $239.30  
  Purchase #3 $102.71   9.748%   $112.7222   $112.72   $112.70   $112.70  
  Purchase #4 $235.28   11.783%   $263.003   $263.00   $263.00   $263.00  
  Purchase #5 $120.96   4.258%   $126.1105   $126.11   $126.10   $126.10  
  Purchase #6 $207.69   11.409%   $231.3854   $231.39   $231.40   $231.40  
  Purchase #7 $68.57   3.496%   $70.9672   $70.97   $70.95   $71.00  
  7 purchase totals = $1,013.08       $1,097.2300   $1,097.23   $1,097.20   $1,097.30