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 $125.34   7.466%   $134.6979   $134.70   $134.70   $134.70  
  Purchase #2 $28.67   11.450%   $31.9527   $31.95   $31.95   $32.00  
  Purchase #3 $106.56   7.617%   $114.6767   $114.68   $114.70   $114.70  
  Purchase #4 $17.50   11.461%   $19.5057   $19.51   $19.50   $19.50  
  Purchase #5 $172.44   6.115%   $182.9847   $182.98   $183.00   $183.00  
  Purchase #6 $35.71   9.176%   $38.9867   $38.99   $39.00   $39.00  
  Purchase #7 $213.33   6.185%   $226.5245   $226.52   $226.50   $226.50  
  7 purchase totals = $699.55       $749.3289   $749.33   $749.35   $749.40